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illystin  No)  121 

LL  S.  DEPARTMENT   QF   AGRICULTURE. 

—  / 

OH'FICE  OF  EXPERIMENT  STATIONS    BULLETIN  NO.  121. 


A.  C.  TRUE,   Director. 


EXTKIJINLTCNTS 


THE  METABOLISM  OF  NITROGEN,  SULPHUR,  AND 

PHOSPHORUS  IN  THE  HUMAN 

ORGANISM. 


lEPOSITORY 


H.  C.  SHERMAN,  Ph.  D., 

Instructor  in  Analytical  Chemistry,  Columbia  University. 


CONDUCTED  IN  COOPERATION  WITH  COLUMBIA  UNIVERSITY. 


WASHINGTON: 

GOVERNMENT     PRINTING     OFFICE, 
1902. 


LIST  OF  PUBLICATIONS  OF  THE  OFFICE  OF  EXPERIMENT  STATIONS  ON 
THE  FOOD  AND  NUTRITION  OF  MAN. 

Note.— For  those  publications  to  which  a  price  is  affixed  application  should  be  made  to  the  Super? 
fntendent  of  Documents,  Union  Building.  Wartiingl  tie  ameer  designated  bylaw 

Government  publications.    Publications  marked  with  an  asterisk  <*)  are  not  available  for  distribution. 

♦Charts.  Food  and  Diet.    By  W.  O.  Atwater.     (Four  charts,  26  by  4<i  inches.)    Price  per  set, 

unmounted,  7.") . 
♦Bui.  21.  Methods  and  Results  of  Investigations  on  the  Chemistry  and  Economy  of  Food.    By 

W   ( )   Atwater.    Pp.  289.    Price,  15  cents. 
Bui.  28.  (Revised  edition.)  The  Chemical  Composition  of  American  Food  Materials.    By  W.  O. 

Atwater  and  A.  P.  Bryant.     Pp.  87.     Price.  5  cents. 
Bui.  2".t.  Dietary  Studies  at  the  University  of  Tennessee  in  1805.    By  C.  E.  Wait,  with  comments 

by  W.  0.  Atwater  and  C.  D.  Woods.     Pp.  45.     Price,  Scents. 
Bui.  81.  Dietary  Studies  at  the  University  of  Missouri  in  1895,  and  Data  Relating  to  Bread  and 

Meat  Consumption  in  Missouri.    By  H.  B.  Gibson,  S.  Calvert,  and  D.  W.  May.  with 

comments  by  W.  O.  Atwater  and  C.  D.  Woods.    Pp.  24.    Price.  5  cents. 
*Bul.  32.  Dietary  Studies  at  Purdue  University.  Lafayette.  Ind.,  in  1895.     By  W.  E.  Stone,  with 

comments  by  W.  O.  Atwater  and  C.  D.  Woods.    Pp.  28.    Price,  5  cents. 
Bui.  35.  Food  and  Nutrition  Investigations  in  New  Jersey  in  1895  and  1896.    By  E.  B.  Voorhees. 

Pp.  40.    Price.  5  cents. 
Bui.  37.  Dietary  Studies  at  the  Maine  State  College  in  1895.    By  W.  H.  Jordan.    Pp.  57.    Price, 

5  cents. 
Bui.  38.  Dietary  Studies  with  Reference  to  the  Food  of  the  Negro  in  Alabama  in  1895  and  1896. 

Conducted  with  the  cooperation  of  the  Tuskegee  Normal  and  Industrial  Institute  and 

the  Agricultural  and  Mechanical  College  of  Alabama.    Reported  by  W.  O.  Atwater 

and  C.  D.  Woods.    Pp.  69.    Price.  5  cents. 
Bui.  40.  Dietary  Studies  in  New  Mexico  in  189o.    By  A.  Goss.    Pp.  23.    Price,  5  cents. 
Bui.  43.  Losses  in  Boiling  Vegetables,  and  the  Composition  and  Digestibility  of  Potatoes  and  Eggs. 

By  H.  Snyder,  A.  J.  Frisby,  and  A.  P.  Bryant.    Pp.  31.    Price,  5  cents. 
BuL  44.  Report  of  Preliminary  Investigations  on  the  Metabolism  of  Nitrogen  and  Carbon  in  the 

Human  Organism  with  a  Respiration  Calorimeter  of  Special  Construction.    By  W.  O. 

Atwater,  C.  D.  Woods,  and  F.  G.  Benedict.    Pp.  64.    Price,  5  cents. 
Bui.  45.  A  Digest  of  Metabolism  Experiments  in  which  the  Balance  of  Income  and  Outgo  was 

Determined.    By  W.  O.  Atwater  and  C.  F.  Langworthy.    Pp.  434.    Price.  25  cents. 
Bui.  46.  Dietary  Studies  in  New  York  City  in  1895  and  1896.    By  W.  O.  Atwater  and  C.  D.  Woods. 

Pp.  117.    Price.  10  cents. 
Bui.  52.  Nutrition  Investigations  in  Pittsburg,  Pa.,  1894-1896.    By  Isabel  Bevier.    Pp.  48.    Price, 

5  cents. 
Bui.  53.  Nutrition  Investigations  at  the  University  of  Tennessee  in  1896  and  1897.    By  C.  E.  Wait. 

Pp.  46.    Price,  5  cents. 
Bui.  54.  Nutrition  Investigations  in  New  Mexico  in  1897.    By  A.  Goss.    Pp.  20.    Price.  5  cents. 
Bui.  55.  Dietary  Studies  in  Chicago  in  1895  and  1896.    Conducted  with  the  cooperation  of  Jane 

Addams  and  Caroline  L.  Hunt,  of  Hull  House.    Reported  by  W.  O.  Atwater  and  A.  P. 

Bryant.    Pp.  76.    Price,  5  cents. 
*  Bui.  56.  History  and  Present  Status  of  Instruction  in  Cooking  in  the  Public  Schools  of  New 

York  City.    Reported  by  Mrs.  Louise  E.  Hogan,  with  an  introduction  by  A.  C.  True, 

Ph.  D.    Pp.  70.    Price.  5  cents. 
Bui.  03.  Description  of  a  New  Respiration  Calorimeter  and  Experiments  on  the  Conservation  of 

Energy  in  the  Human  Body.    By  W.  O.  Atwater  and  E.  B.  Rosa.    Pp.  94.    Price,  10 

cents. 
Bui.  66.  The  Physiological  Effect  of  Creatin  and  Creatinin  and  Their  Value  as  Nutrients.    By 

J.  W.  Mallet.    Pp.  24.    Price.  5  cents. 
Bui.  67.  Studies  on  Bread  and  Bread  Making.    By  Harry  Snyder  and  L.  A.  Voorhees.    Pp.  5L 

Price,  10  cents. 

[Continued  on  third  page  of  cover.] 


L 


:     5.  DEPARTMENT   I  >F    AGRICULTURE. 

O.FIGE  OF  EXPERK,  -   NO.  121. 


A.  C.  TRUE,   D 


EXPERIMENTS 


THE  METABOLISM  OF  NITROGEN,  SULPHUR,  AND 

PHOSPHORUS  IN  THE  HUMAN 

ORGANISM. 


BY 


H.  C.  SHERMAN,  Ph.  D.. 

lor  in  Analytical  Chemistry,  Columbia  Uni 


CONDUCTED   IX   COOPERATION    WITH   COLUMBIA  UNIVERSITY, 


WASH  I  NGTON: 

GOV  E  R N  M  E  N  T     PRINTI'NQ     OFFIC  E  . 

1  9  0  2. 


OFFICE  OF  EXPERIMENT  STATIONS. 

A.  C.  True,  Ph.  D.,  Director. 

E.  W.  Allen,  Ph.  D.,  Assistant  Director  and  Editor  of  Experiment  station  Record. 
C.  F.  Langworthy,  Ph.  D.,  Editor  and  Expert  on  Foods  and  Animal  Production. 

NUTRITION   INVESTIGATIONS. 

W.  O.  Atwater,  Ph.  D.,  Chief  of  Nutrition  Investigations,  Middletown,  Conn. 
C.  D.  Woods,  B.  S.,  Special  Agent  at  Orono,  Mi . 

F.  G.  Benedict,  Ph.  D.,  Physiological  Chemist,  Middletown,  Conn. 
R.  D.  Milner,  Ph.  B.,  Editorial  Assistant,  Middletown,  Conn. 

2 


1 


LETTER  OF  TRANSMITTAL. 


U.  S.  Department  of  Agriculture, 

Office  of  Experiment  Stations, 
Washington,  D.  C.,  October  1,  1902. 
Sir:  I  have  the  honor  to  t  ransmit  herewith  a  report  on  experiments 
on  the  metabolism  of  nitrogen,  sulphur,  and  phosphorus  in  the  human 
organism,  carried  on  by  II.  C.  Sherman,  Ph.  D.,  instructor  in  analyt- 
ical chemistry  at  Columbia  University,  New  York,  in  cooperation  with 
this  Department.  The  investigations  were  conducted  under  the  imme- 
diate supervision  of  Prof.  W.  O.  Atwater,  chief  of  nutrition  investi- 
gations, and  form  a  part  of  the  investigations  on  the  food  of  man 
conducted  under  the  auspices  of  this  Office.  Doctor  Sherman's 
investigations  have  for  their  special  object  a  study  of  the  cleavage  of 
protein,  with  reference  particularly  to  the  waj7  in  which  this  nutrient 
serves  for  building  tissue  and  as  a  source  of  energy.  The  results 
given  herewith  constitute  a  progress  report. 

The  report  is  submitted  with"  the  recommendation  that  it  be  pub- 
lished as  Bulletin  No.  121  of  this  Office. 

Respectfully,  A.  C.  True, 

Director. 
Hon.  James  Wilson, 

Secretary  of  AgricuLtwre. 

3 


CONTENTS. 


Page. 

Introduction 7 

Metabolism  and  elimination  of  sulphur 7 

Metabolism  and  elimination  of  phosphorus 10 

Previous  work  on  the  comparative  metabolism  of  nitrogen,  sulphur, 

and  phosphorus 13 

Purpose  and  plan  of  the  experiments  . _- 15 

Analytical  methods 16 

Composition  of  food  materials 18 

Composition  of  feces 19 

Experiments  on  the  digestibility  of  bread  and  milk 19 

General  description  of  experiments 19 

Digestion  experiment  No.  1 - . .  21 

Digestion  experiment  No.  2 22 

Digestion  experiment  No.  3 23 

Digestion  experiment  No.  4 23 

Digestion  experiment  No.  5 24 

Digestion  experiment  No.  6 25 

Digestion  experiment  No.  7 ■ 25 

Digestion  experiment  No.  8 26 

Digestion  experiment  No.  9 27 

Digestion  experiment  No.  10 . 27 

Results  of  digestion  experiments . .  28 

Comparison  of  the  metabolism  of  nitrogen,  sulphur,  and  phosphorus 31 

Influence  of  loss  of  sleep 34 

Lag  of  elimination  after  change  of  diet 36 

Comparison  of  balance  of  income  and  outgo 43 

Summary 47 

5 


LLUSTRATIOW 


Fig.  1.  Diagram  showing  the  fluctuations  in  the  daily  excretion  of  nitrogen 
and  phosphorus  during  the  first  series  of  experiments  (Nos.  1-3)  - 
Diagram  showing  fluctuations  in  the  daily  excretion  of  nitrogen 
and  phosphorus  during  the  second  series  of  experiments  (Nos.  4 

and  5) 

Diagram  showing  fluctuations  in  the  daily  excretion  of  nitrogen, 
sulphur,  and  phosphorus  during  the  third  series  of  experiments 

(Nos.  7-10)  . 

6 


2. 


3. 


Pa  ire. 


39 


40 


METABOLISM  OF  NITROGEN,  SULPHUR,  AND  PHOSPHORUS  IN 
THE  HUMAN  ORGANISM. 


INTRODUCTION. 

.Most  of  fche  digesl  ion  experiments  heretofore  reported  in  connection 
with  the  nutrition  investigations  of  this  Department  have  included 
the  determination  of  the  balance  of  income  and  outgo  of  nitrogen, 
while  in  those  carried  out  in  the  respiration  calorimeter  the  balance 
of  carbon,  hydrogen,  and  energy  arc  likewise  determined.  It  is 
believed  that  in  many  cases  the  determination  of  income  and  outgo 
of  sulphur  and  phosphorus  will  add  considerably  to  the  interest  and 
value  of  these  investigations. 

The  sulphur  or  phosphorus  balance,  like  the  nitrogen  balance,  may 
be  found  by  comparing  the  amounts  ingested  in  the  food  with  those 
eliminated  through  the  kidneys  and  intestines.  So  far  as  is  known 
no  phosphorus  and  only  traces  of  sulphur  escape  in  the  form  of  vola- 
tile compounds,  and  the  quantities  of  sulphates  and  phosphates  in  the 
perspiration  are  so  small  that  they  may  probably  be  neglected,  unless 
in  exceptional  cases. 

METABOLISM  AND  ELIMINATION  OF  SULPHUR. 

Small  quantities  of  sulphates  occur  in  foods  and  in  some  waters. 

By  far  the  greater  part  of  the  sulphur  of  the  food  enters  the  body  in 
organic    combination,    in    proteids   or   albuminoids.       When  proteid   ^     rj 
matter  is  oxidized  in  the  body  most  of  the  sulphur  is  burned  to  sul- 
phuric acid,  the  greater  part  of  which  appears  in  the  urine  as  normal 
'inorganic  sulphates?)    A  smaller  part  of  the  sulphuric  acid  (in  health 


"usually  about  one-tenth)  is  found  in  the  form  of  ethereal  sulphates, 
i.  e.,  combined  with  organic  radicles,  the  latter  being  usually  regarded 
as  derived  chiefly  from  intestinal  putrefaction  of  proteids.  Such 
putrefaction  may  give  rise  to  the  formation  of  hydrogen  sulphid,  which 
may  either  appear  as  sulphids,  chiefly  of  iron  and  the,  alkali  metals, 
in  the  feces,  or  may  be  absorbed  into  the  system,  or  may  to  some 
extent  escape  with  the  intestinal  gases.  The  total  sulphates  of  the 
urine  may  readily  be  determined  by  precipitation  as  barium  sulphate 
after  boiling  the  urine  with  hydrochloric  acid  to  set  free  the  sulphuric 
acid  in  "ethereal"  combination.  Not  all  of  the  urinary  sulphur, 
however,  exists  in  the  form  of  sulphates.     About  15  to  20  per  cent  is 

7 


8 

usually  found  in  less  completely  oxidized  forms,  this  portion  being 
called  "  unoxidixccl  "  or  ••  neutral"  sulphur,  to  distinguish  it  from  the 
fully  oxidized  sulphate-sulphur.  The  existence  of  sulphur  in  other 
forms  than  sulphates  in  the  urine  was  discovered  by  Ronalds  at 
Giessen  in  1846,°  but  was  first  bronghl  into  prominence  by  Bischoff 
and  Voil  in  Is  .  Several  compounds  have  been  described  as  con- 
tributing  to  the  "neutral"  sulphur  of  the  urine.  The  taurin  of  the 
bile  is  held  to  be  largely  reabsorbed  from  1  he  intestines  and  eliminated 
through  the  kidneys.  If  taurin  be  fed  directly  the  amount  of  neutral 
sulphur  in  the  urine  incr<  jcording  to  Salkowski,"  and  in  experi- 

ments upon  a  dog  with  a  biliary  fistula  the  neutral  sulphur  was  found 
to  decrease,  but  did  not  entirely  disappear.''  Among  other  sulphur 
compounds  which  have  been  found  in  the  urine  maybe  mentioned  sul- 
phocyanids,  originally  derived  from  swallowed  saliva.'  thiosnlphates. 
small  quantities  of  cvstin./  of  mucin,  and  occasionally  of  iiydrogen 
sulphid^  Abel-'  has  described  a  body  which  yields  ethyl  sulphid,  and 
it  is  probable  that  other  compounds  remain  to  be  discovered,  since  the 
quantities  of  the  above  compounds  believed  to  exist  in  normal  urine 
are  not  sufficient  to  account  for  all  of  the  neutral  sulphur  found. 
According  to  Spiegel7'  the  appearance  of  cystin  and  hyposulphites 
in  the  urine  points  to  a  condition  of  diminished  oxidation,  since  these 
compounds  though  constantly  formed  in  the  bod}'  are  not  normally 
end  products  of  metabolism. 

The  following  quotations  from  recent  text-books  (which  are  given  in 
chronological  order)  are  believed  to  fairly  represent  the  present  general 
teachings  in  regard  to  the  significance  of  the  sulphur  metabolism  and 
its  relation  to  the  metabolism  of  nitrogen. 

Halliburton  '  says: 

The  sulphuric  acid  of  the  urine  is  in  part  combined  as  ordinary  sulphates,  in 
part  as  ethereal  sulphates.  It  is  derived  to  a  small  extent  from  the  food,  but 
chiefly  from  the  metabolism  of  proteids,  the  amounts  of  sulphuric  acid  and  urea 
in  the  urine  running  parallel. 

According  to  Hammarsten:^ 

The  sulphuric  acid  of  the  urine  originates  only  to  a  very  small  extent  from  the 
sulphates  of  the  food.     A  disproportioiially  greater  part  is  formed  by  the  burning 

^Falck's  Beitrage  zur  Physiologie,  Hygiene,  etc.,  p.  102. 
&Gesetze  der  Ernahrung  des  Fleischfressers.  pp.  279-284.  302-303. 
I  cCi.  Lusk.  American  Text-book  of  Physiology.  Vol.  I,  p.  507. 
tfKunkel.  Arch.  Physiol.  [Pfluger].  14  (1887),  p.  353. 

^Leared.  Proc.  Royal  Soc.  London.  1870.  pp.  16.  IS:  I.  Musk,  Arch.  Path.  Anat.  u. 
Physiol.  [Virchow].  GO  (1877).  p.  354. 
/G-oldniann  and  Baumann.  Ztschr.  Physiol.  Chem..  12  (1888).  p.  254. 
<7Ztsckr.  Physiol.  Chem  .  '20  (1894).  p.  353. 

*Arch.  Path.  Anat.  u.   Physiol.    [Virchow].  166  (1901),  pp.  364-371:  abs.  in 
Jour.  Chem.  Soc.  [London].  82  (1902),  No.  471.  II.  p. 93. 
MSchaffer's  Text-book  of  Physiology.  Vol.  I.  1898.  p.  79. 
I  J  Text-book  of  Physiological  Chemistry,  trans,  by  J.  A.  Mandel.  1898,  p.  515. 


of  the  proteida  containing  sulphur  within  the  body,  and  it  is  chiefly  this  forma- 
tion of  snlphuric  acid  from  the  proteida  which  gives  rise  to  the  previously  men- 
tioned excess  of  acids  over  the  bases  in  the  arine.  The  quantity  of  snlphnric  a  id 
eliminated  by  the  urine  amounts  to  2.5  grams  B8SO<per24  hours.  As  the  sul- 
phuric arid  chiefly  originates  from  the  proteids,  it  follows  that  the  elimination  of 
sulphuric  acid  and  the  elimination  of  nitrogen  arc  nearly  parallel,  and  the  rela- 
i  ionship  X  :  II. so,  i<  :ii>.nii  !„■')  •  l-  A  complete  parallelism  ran  hardly  be  expected, 
as  in  tin-  first  place,  a  pari  »>t'  the  sulphur  is  always  eliminated  as  neutral  sulphur, 
and  secondly,  because  the  low  quantity  of  sulphur  in  different  protein  bodies 
undergoes  greater  variation  as  compared  with  the  high  quantity  of  nitrogen  con- 
tained therein.  Generally  the  relationship  between  the  elimination  of  nitrogen 
and  sulphuric  acid  under  normal  and  d  seased  conditions  runs  rather  parallel. 

In  Novy's"  opinion: 

The  proteins  of  the  food  and  of  the  tissues  constitute  almost  the  sole  source  of 
the  sulphur  containing  waste  products.  A  small  amount  of  waste  sulphur  com- 
pounds is  eliminated  as  sulphocyauate  by  the  saliva,  gastric  juice,  etc.  Another 
small  portion  leaves  the  body  as  taurin  in  the  taurocholic  acid  of  the  bile.  With 
these  exceptions  almost  all  the  sulphur  resulting  from  protein  disintegration 
appears  in  the  urine.  Inasmuch  as  the  sulphates  contain  most  of  the  waste  sul- 
phur it  follows  that  the  total  sulphates  in  the  urine  furnish  an  excellent  index  of 
proteid  disintegration. 

According  to  Ogden : b 

The  total  quantity  of  sulphuric  acid  in  the  twenty-four  hours'  amount  of  urine 
of  an  adult  taking  a  mixed  diet  is  from  1.}  to  3  grams,  or  an  average  of  2  grams. 
About  one-tenth  of  the  total  sulphuric  acid  is  in  the  form  of  ethereal  sulphates. 
In  general  it  may  be  stated  that  the  variation  in  the  quantity  of  ordinary  sulphates 
eliminated  in  the  urine  runs  parallel  to  that  of  urea. 

Lusk.c  states  that : 

Sulphur  is  built  in  the  proteid  molecule  of  the  plant  from  the  sulphates  taken 
from  the  ground.  It  is  found  in  albuminoids,  especially  in  keratin.  As  taurin 
it  occurs  in  muscle  and  in  bile,  as  iron  and  alkaline  sulphids  in  the  feces,  as  sul- 
phureted  hydrogen  in  the  intestinal  gas,  as  sulphate  and  other  unknown  com- 
pounds in  the  urine.  *  *  *  The  total  amount  of  sulphur  in  the  urine  runs  icu^^f*  2 
proportionately  parallel  with  the  amount  of  nitrogen;  that  is  to  say,  the  amount  1^^'  t 
is  proportional  to  the  amount  of  proteid  destroyed.  *  *  *  When  an  animal 
eats  proteid  and  neither  gains  nor  loses  the  same  in  his  body,  the  amount  of  sul- 
phur is  equal  to  the  sum  of  that:  found  in  the  urine  and  feces.  Sulphates  eaten 
pass  out  through  the  urine.     They  play  no  part  in  the  life  of  the  cell. 

Thus  there  is  general  agreement  in  regarding  the  sulphur  of  the 
urine  as  essentially  derived  from  katabolism  of  proteid  in  the  body, 
so  that  the  quantity  eliminated  is,  like  that  of  nitrogen,  an  indication 
of  the  amount  of  proteid  matter  broken  down.  This  agreement  in 
regard  to  the  parallelism  of  the  nitrogen  and  sulphur  excretion  is, 
however,  by  no  means  exact,  since  in  some  cases  the  reference  is  to 
total  sulphur,  in  others  to  total  sulphates,  and  in  still  others  to  "ordi- 
nary "  sulphates. 

«  Physiological  Chemistry,  second  ed.,  1898,  pp.  194.  195. 

&  Clinical  Examination  of  the  Urine,  1900,  p.  111. 

<•  American  Text-book  of  Physiology,  second  ed..  Vol.  I.  1900.  pp.  505,  507. 


10 

Of  the  authors  quoted.  Hammarsten  is  the  only  one  to  call  atten- 
t  ion  to  the  fact  thai  this  parallelism  will  be  affected  by  the  variations 
in  the  relative  proportions  of  nitrogen  and  sulphur  in  different  pro- 
teids.  Thai  these  variations  are  very  large  will  be  seen  from  a  com- 
parison of  the  accepted  analyses  of  a  few  representative  proteids. 
Taking,  for  Instance,  the  elementary  analyses  recently  compiled  by 
Osborne  in  connection  with  his  discussion  of  the  sulphur  in  proteid 
bodies,"  Ave  estimate  from  the  percentages  given  thai  the  ratio  of 
nitrogen  to  sulphur  is,  in  jegumin as  L6.9:  1 ;  in  f.cin.  26.9:  1  ;  in  edeatin. 
21.2:1;  in  bynin,  19.4:1;  In  ffliadin,  L7.2: 1;  and  in  leucosin,  13.1:1. 
From  this  it  will  appear  thai  the  typical  proteids  oi  wheat  furnish 
about  three  times  as  much  sulphur,  with  a  given  amount  of  nitrogen, 
as  the  typical  proteid  of  the  legumes.  The  ratio  in  casein  (19.7:1)  is 
about  twice  as  great  as  in  egg  albumin  (9.6:  J).  Among  the  proteid 
constituents  of  the  body  the  differences  are  even  greater  than  among 
the  food  proteids  just  mentioned.  In  oxyhemoglobin  the  ratio  is 
44.6:1;  in  myosin,  13.1:1;  in  serum  globuJrtn.  14.3:  lj  in  fibrinogen, 
13.3:1;  in  serum  albumin  from  human  exudation,  7.06:1;  in  chon- 
droniucoid/  5.2:1;  in  tendon-mucin/  5:1,  and  in  osseomucoid,6  5: 1. 

Thus  it  would  appear  that  the  katabolismof  sufficient  glucoproteid 
to  yield  a  gram  of  nitrogen  would  result  in  the  elimination  of  about 
three  times  as  much  sulphur  as  the  katabolism  of  an  equivalent 
amount  of  myosin,  serum  globulin,  or  gliadin,  and  nearly  ten  tines 
as  much  as  would  come  from  an  equivalent  amount  of  oxyhemoglo- 
bin or  of  legumin.  It  is  evident,  therefore,  that  the  ratio  of  nitrogen 
to  sulphur  in  the  urine  may  undergo  considerable  variation  as  the 
result  of  changes  in  the  kind  of  proteid  given  in  the  food  or  in  the 
kind  of  body  tissue  katabolized  in  case  the  protein  of  the  food  is 
insufficient.  The  interesting  investigations  of  Kolpatcka  noted  below 
(p.  13)  are  based  largely  on  these  variations.  There  is,  however, 
everjr  reason  to  believe  that  so  long  as  the  diet  is  uniform,  and  othe] 
conditions  normal,  the  metabolism  and  elimination  of  sulphur  wil 
be  nearly  parallel  with  that  of  nitrogen ;  and  this  seems  to  be  true  not 
only  as  concerns  the  twenty-four  hours'  urine,  but  usually  for  shorter 
periods  as  well.     (See  p.  45.) 

METABOLISM  AND  ELIMINATION  OF  PHOSPHORUS. 

Phosphorus  enters  the  body  in  organic  combination  in  the  form  of 
nucleins,  nucleo-proteids,   lecithin,  protagon,  and  perhaps  glycerol- 

« Connecticut  State  Sta.  Rpt.  1900,  p.  464:  Jour.  Amer.  Chem.  Soc,  24  (1902), 
p.  140. 

b  The  ratios  given  for  the  glucoproteids  are  from  figures  given  by  Hawk  and 
Gies  (Amer.  Jour.  Physiol.,  5  (1901),  p.  416.  In  the  case  of  osseomucoid  the  aver- 
age of  the  later  and  purer  preparations  is  taken.  The  figures  for  tendon-mucin 
(Chittenden  and  Gies)  have  recently  been  confirmed  by  Cutter  and  Gies  (Amer. 
Jour.  Physiol. .  6  (1902) .  p.  155.  The  figures  for  chondromucoid  are  from  the  work 
of  Morner  (Ztschr.  Physiol.  Chem..  18  I  L893),  p.  213, 


11 

phosphoric  acid,  but  a  Larger  quanl  ity  i<  taken  as  mineral  phosphates 
in  the  food.  The  proportion  of  phosphorus  eliminated  by  the  intes^ 
tine  depends  mainly  on  the  nature  of  the  food  and  the  alkalinity  or 
the  blood.     Berbivora  excrete  nearly  all  of  the  phosphorus  with  the 

feces,  and  in  man  1  he  amount  1  h  us  excreted  is  greatest  on  a  vegetable 
diet  or  one  rich  in  lime  salts,  and  may  he  Largely  increased  by  feed- 
ing alkaline  cit  rate  and  calcium  carbonate,  the  first  to  furnish  the 
more  alkaline  reaction  to  the  blood  and  urine,  the  second  to  form  with 
the  phosphoric  acid  the  insoluble  phosphate  of  lime  (Lusk).a 
/  The  phosphorus  of  the  urine  is  present  chiefly  as  phosphates  of  I 
/tin'  alkalies,  with  a  much  smaller  quantity  of  phosphates  of  they 
alkaline  earths.  A  very  small  proportion  is  present  in  organic  com- 
bination^ This  has  been  believed  to  exist  as  glycerol-phosphoric 
acid.  Jolly/'  however,  claims  to  have  found  in  the  urine  certain 
peculiar  nitrogenous  compounds,  which  retain  some  mineral  phos- 
phate in  such  intimate  association  that  the  phosphoric  acid  is  not 
precipitated  by  the  usual  reagents,  and  he  believe^  that  it  is  these 
phosphates  and  not.  glycerol-phosphoric  acid  or  any  incompletely  oxi- 
dized form  of  phosphorus  which  escapes  precipitation  by  the  ordinary 
methods. 

Since  t lie  phosphorus  of  the  urine  comes  so  largely  from  the  simple 
passage  through  the  system  of  the  phosphates  taken  in  the  food,  it 
follows  that  variations  in  the  quantity  eliminated  are  more  apt  to 
be  connected  with  the  diet  than  with  the  metabolism  of  bod}T  mate- 
rial. The  idea  once  held  that  the  quantity  of  phosphorus  eliminated 
is  principally  dependent  upon  the  metabolism  of  nervous  tissue  was 
soon  abandoned.  In  this  connection  Voit*  stated  that  the  bones 
contain  about  1.400  grams  of  phosphorus,  the  muscles  about  130 
grams,  and  the  brain  and  nervous  sj'Stem  about  12  grams.  Moreover, 
by  comparing  the  loss  of  weight  of  different  organs  in  the  starving 
dog.  with  the  changes  in  the  ratio  of  nitrogen  to  phosphorus  in  the 
urine,  he  was  able  to  show  that  the  body  material  katabolized  was 
largely  contributed  by  the  bones. 

Recent  work  tends  to  emphasize  the  importance  of  the  nucleins  and 
related  bodies  and  to  confirm  the  view  thai  the  phosphates  found  in 
all  the  organs  and  tissues  of  the  body  are  to  a  considerable  extent  in 
chemical  combination  with  the  proteid  matter.  Thus  it  is  stated  that, 
when  the  body  stores  proteid  a  proportionate  amount  of  phosphoric 
acid  is  retained  for  the  new  protoplasm,  while  on  destruction  of  pro- 
teid the  phosphoric  acid  corresponding  to  it  is  eliminated. d 

«See  also  the  recent  work  of  Paton  and  his  associates  (Jour.  Physiol..  25  (1900), 
p.  212),  comparing  the  metabolism  and  elimination  of  phosphorus  in  the  dog  and 
in  the  goat. 

»Conipt.  Rend.  Acad.  Sci.  Paris.  127  i  1898),  118. 

<" Hermann's  Handhnch  des  Physiologic  vol.  6.  pt.  1,  p.  80. 

'Lnsk.  American  Text-book  of  Physiology,  second  ed..  1900.  Vol.  I.  p.  575. 


12 

Hie  significance  of  the  phosphorus  metabolism  from  the  medical 
standpoint  is  quite  fully  discussed  by  Bergell.* 

Several  investigators*  have  recently  studied  the  urinary  excretion 
of  phosphates  as  influenced  by  those  conditions  which  are  believed  to 
be  especially  connected  with  the  met al >ol ism  of  nudeins. 

An  intimate  connection  between  changes  in  the  phosphorus  elimi- 
nated and  in  the  kaiab  >lism  of  nueleins  is  evidently  assumed  by 
Dunlop,  Paton,  Stockmann,  and  Maccadam  in  interpreting  the  results 
of  their  investigations  of  the  effects  of  muscular  exertion/  In  these 
experiments  each  subject  maintained  a  uniform  diet  for  seven  days. 
on  the  fourth  of  which  as  much  exercise  (bicycle  riding)  was  taken  as 
the  subject  could  endure  without  serious  discomfort.  In  each  case 
the  day  or  days  following  the  exertion  showed  an  increased  elimina- 
tion of  nitrogen  and  sulphur,  but  only  when  the  subject  was  in  poor 
training  was  there  a  corresponding  increase  in  the  elimination  of 
phosphates  and  of  uric  acid.  From  this  it  was  concluded  that  with 
the  -subject  in  good  training  only  muscle  proteid  is  broken  down, 
while  if  the  subject  be  in  poor  training  this  consumption  of  muscle 
proteid  is  accompanied  b}T  the  consumption  of  the  material  of  other 
tissues  which  contain  nucleo-proteid.  In  this  connection  it  is  inter- 
esting to  note  the  observation  previously  made  by  Preysz,(/  that  the 
increased  elimination  of  phosphoric  acid  resulting  from  walking  a  given 
distance  (2d  kilometers)  was  considerably  greater  when  the  distance 
was  walked  at  a  rapid  rate,  causing  a  more  intense  though  less  pro- 
longed exertion. 

As  already  stated,  the  greater  part  of  the  phosphorus  eliminated 
comes  from  the  phosphates  of  the  food.  fwhen,  however,  the  diet  is 
uniform,  a  variation  in  the  phosphorus  elimination  must  be  taken  as 
showing  some  change  either  in  body  metabolism  or  in  the  condition  of 
the  body  with  reference  to  its  store  of  phosphates^  Whether  or  not 
the  connection  between  urinary  phosphates  and  the  katabolism  of 
nueleins  is  as  intimate  as  some  investigators  seem  to  assume,  it  is  evi- 
dent that  the  study  of  the  phosphorus  balance  may  give  valuable 
information  which  could  not  otherwise  be  obtained  regarding  the 
nature  of  the  changes  taking  jjlace  in  the  body. 

«Fortschr.  Med.,  1G  (1898),  p.  1.  Bedeutung  der  Phosphorsaure  in  mensch- 
lichen  und  thierschen  Organisuien.     Inaug.  Diss..  Berlin.  1898. 

'Oloraczewski.  Arch.  Path.  Anat.  vi.  Physiol.  [VirchowJ .  151  (1898).  p.  88; 
Milroyand  Malcolm.  Jour.  Physiol..  23  (1898),  p.  817,  audio  (1899).  p.  103:  White 
and  Hopkins.  Ibid..  24  (1899).  p.  42:  Loewi.  Ar<  h.  Exper.  Path.  u.  Pharmakol..  44 
(1900-1901),  p.  1:  abs.  in  Jour.  Chem.  Soc.  [London].  78.  1900.  II.  p.  417. 

ejour.  Physiol..  22  (1897-98).  p.  68. 

tfUngar,  Arch,  Med..  1  (1892-93),  p.  38:  reviewed  in  Arch.  Physiol.  [Pfltiger]. 
54  (1893),  p.  81. 


18 

PREVIOUS   WORK   ON   THE    COMPARATIVE    METABOLISM   OF 
NITROGEN,   SULPHUR,  AND  PHOSPHORUS. 

The  coursi  of  tlu  elimination  during  tin  day.  —Considerable  atten- 
tion lias  been  given  by  differenl  investigators  to  tin'  course  of  the 
elimination  of  nitrogen  and  of  phosphorus  daring  the  day.  The 
recent  work  of  Rosemanna  on  nitrogen  and  of  his  pupil  Roeske*  on 
phosphorus  may  be  especially  aoted.  (Jnfortunately  such  studies 
have  usually  been  made  upon  only  one  element  at  a  time.  In  some 
recent  experiments  carried  out  in  the  Laboratories  of  Wesleyan  Univer- 
sity' the  course  of  elimination  of  nitrogen,  sulphur,  and  phosphorus 
has  been  observed  simultaneously,  the  urine  being  collected  in  the 
three- hour  periods  during  the  day  with  one  nine-hour  period  at  night. 
The  rates  of  elimination  of  nitrogen  and  sulphur  were  found  to  run 
nearly  parallel,  rising  and  falling  twice  during  the  day  and  reaching 
a  minimum  during  the  night.  The  fluctuations,  though  quite  reg- 
ular, were  not  very  great,  the  highest  rate  of  elimination  found  dur- 
ing the  day  being  usually  about  one-fourth  greater  than  the  average 
rate  for  the  nine  hours  of  the  night.  The  elimination  of  phosphorus, 
on  the  other  hand,  did  not  run  parallel  witli  that  of  nitrogen  and 
sulphur,  and  the  fluctuations,  though  less  regular,  were  considerably 
larger,  the  maximum  rate  of  elimination  being  two  to  three  times  as 
great  as  the  minimum.  Moreover,  the  minimum  rate  of  elimination 
of  phosphorus  was  reached  not  during  the  night,  but  at  some  time  in 
the  forenoon,  usually  from  one  to  three  hours,  but  sometimes  from 
four  to  six  hours  after  rising. 

Comparativt  metabolism  during  periods  of  a  day  or  more. — Many 
metabolism  experiments  have  been  made  in  which  nitrogen  and  phos- 
phorus were  determined  and  a  smaller  number  in  which  sulphur  was 
also  included.  Several  of  these  investigations  will  be  referred  to  later 
in  connection  with  the  discussion  of  the  results  of  experiments  here 
report e< I.  The  investigations  of  Kolpatckad  are,  however,  so  sugges- 
tive that  they  should  be  mentioned  here.  The  subjects  were  in  all  cum^ 
dogs,  and  the  object  of  the  work  was  to  learn  the  real  source  of  the 
nitrogen  in  the  urine — to  determine  whether  it  is  derived  directly  from 
the  protein  of  the  food,  from  protein  stored  in  the  body,  or  from  actual 
proteid  tissue — and  further,  to  study  the  nature'of  the  stored  protein. 

Arch.  Physiol.  [Pfluger],  66  (1896),  p.  343. 

•ber  den  Verlauf  der  Phosphorsaure  Ausscheidung  beim  Menschen.     Inaug. 
Diss.,  Greifswald,  1897. 

c Sherman  and  Hawk,  Amer.  Jour.  Physiol..  4  (1900).  p  25,  and  unpublished 
results  by  At  water  and  Hawk  and  by  Hawk  and  Chamberlain..  These  experi- 
ments are  more  fully  described  in  connection  with  the  discussion  of  "lag"  on 
p.  36. 

(l Phiziologicheskii  Sbornik.  A.  I.  and  V.  I.  Danilevski.  editors.  Kharkov, 
1888,  Vol.  I.  p.  33;  abs.  in  U.  S.  Dept.  Agr.,  Office  of  Experiment  Stations  Bui.  45, 

pp.  308,  m 


14 

Kolpatcka  endeavored  to  solve  these  problems  by  comparing  the 
ratios  of  phosphoric  acid  to  nitrogen  and  of  sulphur  to  nitrogen  in 
the  food  consumed  and  in  the  urine.  The  ratios  found  in  the  foods 
osed   were  as  follows:    In   meat,  P805:N::  1:7.3;    S:N::  1:15.6.      In 

gelatin,  which  contains  no  P.>05,  the  ratio  Is  as  follow-:  S:N::  L:22.5. 
In  white-  of  eggs,  P205:X::  1:47.6;  S:X::1:  9.8.  In  yolks  of  eggs, 
1'  «  l  :  X::  1:  L.8.  Knowing  the  ratios  of  these  elements  in  the  food 
and  in  the  urine  during  partial  or  complete  fasting,  it  was  held  to  be 
possible  to  judge  whether  the  nitrogen  in  the  urine  for  any  particular 
period  came  from  the  food  consumed,  from  stored  protein,  or  from 
actual  body  tissue.  Thus  on  a  meat  diet  the  ratio  of  P205:X  in  the 
urine  was  nearly  the  same  as  in  the  food,  and  it  was  concluded  that 
the  excreted  nitrogen  came  directly  from  the  food.  During  a  period 
of  lasting  following  the  meat  diet  the  relative  proportion  of  phosphorus 
excreted  gradually  increased  until  the  fifth  day,  after  which  the  ratio 
was  nearly  constant.  P.,05:  X::  1:  4  (about).  A  similar  change  in  the 
ratio  was  found  after  a  change  from  meat  diet  to  a  diet  of  fat  and 
starch.  These  results  are  held  to  show  that  when  the  supply  of  pro- 
tein is  cut  off  there  follows  a  katabolism,  first  of  protein  simply 
stored  from  the  previous  diet  and  not  yet  organized,  then  of  protein 
from  body  tissue,  this  last  being  the  sole  source  after  the  fifth  day 
and  yielding  a  relatively  large  proportion  of  phosphorus.  The 
increased  proportion  of  "earthy"  phosphates  led  to  the  belief  that 
some  of  the  "tissue  protein"  came  from  the  bones,  a  conclusion 
reached  several  years  ago  by  Voit.     (See  p.  11.) 

On  passing  from  a  meat  ration  to  a  ration  of  white  of  egg  there  was 
a  diminution  of  phosphoric  acid  and  an  increase  of  sulphur.  The 
ratios,  however,  varied  considerably,  and  a  relatively  large  amount  of 
phosphoric  acid  in  the  first  <lays  was  attributed  to  a  destruction  of 
some  body  protein.  In  passing  from  a  meat  to  a  gelatin  ration  the 
amount  of  nitrogen  in  the  urine  increased,  while  the  amount  of  phos- 
phoric acid  decreased  but  did  not  entirely  disappear,  thus  giving 
additional  evidence  that  gelatin  alone  can  not  prevent  the  breaking 
down  of  protein  tissue.  In  several  cases  the  experiments  were 
repeated  with  substantially  the  same  result.  So  far  as  can  be  judged 
from  the  available  data  of  these  experiments,  some  factors  seem  to 
have  been  overlooked  by  Kolpatcka  which  would  affect  the  interpre- 
tation of  the  results.  Among  these  is  the  '"lag"  in  the  excretion  of 
the  products  of  metabolism,  which  would  have  an  important  influence 
upon  the  changes  in  the  urine  following  a  change  in  the  ration,  or 
during  the  first  days  of  fasting.  Moreover,  the  lag  may  be  different 
for  the  three  elements  under  discussion,  and  these  differences  may  be 
influenced  by  the  nature  of  the  diet.  The  amounts  of  nitrogen,  sul- 
phur, and  phosphorus  in  the  feces  are  recorded  but  do  not  seem  to 
have  been  included  in  determining  the  ratios.  These  quantities  were 
generally  not  large,  but  in  several  cases  the  phosphorus  of  the  feces 


15 

was  over  LO  per  oenl  of  the  total  excretion.  The  phosphoric  acid 
determinations  were  in  all  cases  mad*'  by  til  ration  with  uranium  ace- 
tate. For  nrine  this  may  be  considered  fairly  satisfactory;  with  meat 
and  other  materials  containing  appreciable  amounts  of  iron  the  errors 
might  be  larger.  Thus  this  investigation,  while"  of  .ureal  value  and 
certainly  rich  in  interest  and  suggestion,  seems  to  ueglecl  some  fac- 
tors which  are  still  in  need  of  investigation  and  which  may  appreci- 
ably affect  the  interpretation  of  the  results  obtained.  These  factors 
would  be  of  even  greater  importance  in  experiments  upon  the  human 
subject,  where  either  the  balance  of  income  and  outgo  or  the  "lag," 
or  both,  may  be  more  or  less  influenced  by  the  mental  and  nervons 
condition,  ami  w  here  often  a  much  Larger  proportion  of  the  phosphorus 
Leaves  the  body  through  the  feces.  If  this  fecal  phosphate  is  an  indi- 
gestible residue  il  should  be  deducted  from  the  amount  in  the  food 
before  calculating  the  ratios  discussed  above.  If,  on  the  other  hand, 
it  has  been  metabolized  and  excreted  into  the  intestine,  it  should  be 
added  to  the  amount  eliminated  in  the  urine.  Much  work  is  being 
done  in  the  attempt  to  distinguish  between  the  nitrogen  of  undigested 
residues  and  that  of  metabolic  products.  In  the  case  of  phosphorus 
this  distinction  is  of  greater  relative  importance,  because  the  per- 
centage of  the  ingested  phosphorus  eliminated  in  the  feces  is  apt  to 
be  much  Larger  than  that  of  the  ingested  nitrogen. 

PURPOSE  AND  PLAN  OF  THE  EXPERIMENTS. 

The  work  here  reported  comprises  10  experiments  with  man  on  a 
milk  and  bread  diet,  in  each  of  which  the  digestibility  of  the  nutrients 
of  the  food  and  the  income  and  outgo  of  nitrogen,  sulphur,  and  phos- 
phorus were  determined.  In  most  cases  two  or  more  experiments 
were  arranged  in  scries,  so  that  the  change  in  diet  gave  an  opportunity 
to  determine  whether  the  alteration  in  the  excretion  occurred  simul- 
taneously for  the  three  elements  studied;  in  other  words,  to  compare 
the  "lag"  of  sulphur  and  of  phosphorus  with  that  of  nitrogen.  The 
general  purpose  of  the  study  was  thus  twofold — to  accumulate  addi- 
tional determinations  of  the  digestibility  of  bread  and  milk  diet,  and 
by  collecting  data  regarding  the  comparative  metabolism  of  nitrogen, 
sulphur,  and  phosphorus  to  prepare  the  way  for  the  study  of  the  latter 
elements  in  connection  with  certain  of  the  nutrition  investigations 
carried  on  by  the  Department  of  Agriculture.  Attention  has  there- 
fore been  mainly  directed  to  points  which  of  themselves  might  not  be 
of  much  interest,  but  which  arc  likely  to  influence  the  methods  of 
experimenting  or  tin'  interpretation  of  the  results.  Among  these 
points  may  be  mentioned  the  question  of  "lag"  already  referred  to, 
the  influence  of  a  change  of  routine,  such  as  marked  loss  of  sleep,  the 
gain  or  Loss  of  sulphur  and  phosphorus  while  the  body  is  gaining  or 
Losing  nitrogen,  the  proportion  of  urinary  sulphur  in  forms  other  than 
sulphates  and  of  phosphorus  in  forms  other  than  phosphates,  and  the 


16 

question  whether  the  large  proportion  of  phosphorus  which  leaves  the 
body  by  the  feces  is  incapable  of  absorption,  or  is  not  absorbed  because 
not  needed,  or  has  been  metabolized  in  the  body  and  excreted  through 
the  intestine. 

For  convenience  of  reference  the  digestibilities  of  the  nutrients  in 
the  different  experiments  are  first  reported  in  the  form  which  has 
been  followed  in  previous  bulletins  of  this  series,  after  which  the 
metabolism  of  nitrogen,  sulphur,  and  phosphorus  is  discussed  in  a 
separate  section. 

ANALYTICAL  METHODS. 

All  food  materials  used  in  the  investigation  were  sampled  at  the 
time  of  use  and  all  the  feces  were  collected,  dried,  and  analyzed. 
The  methods  of  analysis  were  mainly  those  of  the  Association  of  Offi- 
cial Agricultural  Chemists.0  The  determination  of  ether  extract  in 
the  feces  gave  in  some  cases  variable  results  and  is  nor,  considered 
entirely  satisfactory.  The  bread  (soda  crackers)  and  butter  used  in 
the  experiments  were  generally  prepared  in  advance  in  sufficient  quan- 
tity for  several  experiments,  thus  reducing  the  number  of  analyses 
required.  The  milk  used  was  obtained  by  mixing  the  entire  product 
of  a  small  local  herd  and  was  delivered  in  bottles.  Previous  experi- 
ence had  shown  that  the  milk  obtained  from  this  source  was  almost 
uniform  from  day  to  day.  In  the  present  experiments  a  composite 
sample  was  prepared  for  each  experimental  period  by  taking  a  pro- 
portionate amount  of  the  milk  at  the  time  of  weighing  the  portion  for 
each  meal.  In  the  fresh  sample  for.  each  period  the  nitrogen  and 
either  the  fat  or  the  total  solids  was  determined,  after  which  a  portion 
was  dried,  ground,  and  submitted  to  complete  analysis.  In  case  the 
partial  analyses  of  samples  of  milk  used  in  successive  experiments  of 
a  continuous  series  showed  no  greater  differences  than  occur  in  dupli- 
cate determinations  on  a  single  sample,  the  dried  residues  were  ground 
together  into  a  single  composite  sample  for  complete  analysis. 

Heat  of  combustion  was  determined  by  means  of  the  Atwater- 
Blakeslee  bomb  calorimeter,  as  described  in  previous  publications,6 
urine  being  previously  dried  on  blocks  of  cellulose  in  the  usual 
manner.0 

Sulphur  in  foods  and  feces  was  oxidized  to  sulphuric  acid,  some- 
times by  fusion  with  sodium  hydroxid  and  potassium  nitrate  in  the 
usual  manner  and  sometimes  by  burning  the  material  in  the  bomb 
calorimeter.  The  latter  method  is  quicker  and  more  convenient  in 
every  way  and,  so  far  as  we  have  employed  it,  gives  the  same  results 
as  the  alkaline  fusion  method.     The  method  of  oxidation  in  the  bomb 

oil.  S.  Dept.  Agr..  Division  of  Chemistry  Bnl.  46. 

&U.  S.  Dept.  Agr.,  Office  of  Experiment  Stations  Bui.  21,  p.  120:  Connecticut 
Storrs  Sta.  Rpt.  1897,  p.  199. 

<"Land\v.  Vers.  Stat.,  47  (1896).  p.  297:  U.  S.  Dept.  Agr.,  Office  of  Experiment 
Stations  Bui.  69,  p.  23. 


17 

as  here  used  was  practically  an  adaptation  of  that  given  by  Hempel.a 
The  substance  was  pressed  into  a  pellel  anil  burned  in  the  same 
manner  as  in  determining  the  heal  of  combustion;  then  by  means  of 
a  special  coupling  the  gas  in  the  bomb  was  allowed  to  escape  slowly 
through  an  outlet  tube  having  very  narrow  bore  and  was  passed 
through  bromin  water  in  a  U-tube  containing  glass  beads.  The 
moisture  condensed  on  the  cover  and  Lining  of  the  bomb  was  thor- 
oughly washed  (tui  and  united  with  the  bromin  water  and  rinsings 
from  the  LMube,  more  bromin  water  added,  if  necessary,  and  the 
solution  boiled  to  insure  the  oxidation  to  sulphuric  acid  of  any  sul- 
phurous acid  which  may  have  been  formed.  The  platinum  capsule 
in  which  the  pellel  was  burned  was  placed  in  a  small  beaker  and 
heated  with  hydrochloric  acid,  to  dissolve  any  sulphates  in  the  ash.8 
This  solution  was  Then  added  to  the  one  jusl  mentioned  and  the  whole 
filtered  and  precipitated  with  barium  chlorid  in  the  usual  manner. 
As  the  solution  always  contained  some  iron  from  the  igniting  wire 
and  the  precipitates  of  barium  sulphate  were  small  and  formed  slowly, 
the  latter  were  allowed  to  stand  overnight  in  the  cold  before  filter- 
ing. In  the  work  here  reported  this  method  was  used  only  to  check 
some  of  the  results  obtained  by  the  fusion  method,  but  it  has  since 
been  studied  in  some  detail  (see  below). 

In  oxidizing  the  sulphur  of  foods  and  feces  by  the  usual  fusion 
method,  from  1  to  3  grams  of  sample  was  melted  with  7  to  12  grams 
of  sodium  hydroxid  containing  a  little  potassium  nitrate;  afterwTards 
more  nitrate  was  added  in  small  portions  until  the  oxidation  was 
complete.  The  fusions  were  made  in  silver  vessels  heated  by  alcohol 
lamps.  The  fused  mass  after  cooling  was  dissolved  in  water  and 
twice  evaporated  to  dryness  with  excess  of  hydrochloric  acid,  after 
which  it  was  taken  up  with  acidulated  water  and  precipitated  in  the 
usual  way.  In  estimating  the  total  sulphur  in  urine,  -40  cubic  centi- 
meters were  evaporated  to  dryness  in  a  silver  dish  or  crucible  and 
the  residue  treated  as  just  described.  The  amount  of  sulphur  intro- 
duced by  the  reagents  used  was  determined  and  the  corresponding 
corrections  applied  to  the  results  obtained. 

For  the  determination  of  phosphorus  the  material  was  oxidized  either 
by  means  of  caustic  soda  and  potassium  nitrate  in  the  same  manner 
as  for  the  determination  of  sulphur,  or  by  fusion  with  sodium  carbon- 
ate and  potassium  nitrate  in  a  similar  manner.  In  the  latter  case  the 
fusion  was  made  in  a  platinum  dish  over  a  Bunsen  burner.  In  either 
ease  the  fused  mass  after  cooling  was  dissolved  in  water,  treated  with 

"Ber.  Deut.  Chem.  Gesell..  30  (1897).  p.  202. 

&In  the  presence  of  barium  sulphate  it  would,  of  course,  be  necessary  to  fuse 
this  residue.  In  the  ordinary  foods  it  seems  safe  to  assume  the  absence  of  appre- 
ciable quantities  of  barium. 

usi;i_  Xo.  121—02 2 


18 

nitric  acid  in  considerable  excess,  and  the  solution  boiled  down  to 
small  bulk,  after  which  ii  was  diluted,  filtered  if  necessary,  and  the 
phosphoric  acid  determined  by  the  molybdate-magnesia  method,  fol- 
lowing the  details  adopted  by  the  Association  of  Official  Agricultural 
Chemists  and  using  special  care  to  insure' the  purity  of  the  final 
precipitate. 

The  si  inly  of  methods  for  the  determination  of  sulphur  and  phos- 
phorus has  been  continued  since  the  completion  of  the  experiments 
described  in  the  bulletin.  A  comparison  of  the  method  of  fusion  with 
alkali  and  an  oxidizing  agent  with  that  of  combustion  in  oxygen 
showed  practically  identical  results  in  the  determination  of  sulphur 
and  confirmed  our  preference  for  the  latter  method. 

In  the  determination  of  jdiosphorus  practically  the  same  results 
were  obtained  whether  the  material  was  oxidized  by  means  of  carbon- 
ate and  nitrate  as  above  described,  by  combustion  in  oxygen  as  in 
the  determination  of  sulphur,  or  by  boiling  with  sulphuric  acid  and 
ammonium  nitrate. 

The  details  of  this  study  of  methods  have  been  published  else- 
where.0 

COMPOSITION  OF  FOOD  MATERIALS. 

The  milk  used  has  already  been  described.  For  bread  the  material 
selected  was  commercial  "soda  crackers"  or  "soda  biscuit,"  these 
being  readily  obtainable  of  practically  uniform  composition  and  easily 
kept  without  undergoing  change  or  becoming  distasteful.  The  butter 
was  an  ordinary  product  of  good  quality.  The  analyses  of  the  food 
materials  are  given  in  Table  1. 

Table  1. — Composition  of  food  materials. 


Labo- 
ratory 
num- 
ber of 
sam- 
ple. 


Material. 


Water 


Nitro- 


Pro- 


tern  i  N 
gen-     x6.25). 


Car- 
Fat,     bohy- 
drates. 


Ash. 


En- 
ergy 

per 
gram. 


Sul- 
pbur. 


650 
651 
652 
653 
654 
< '..V) 
656 
657 
658 


Crackers  (experi- 
ments Nos.  1-5) 

Milk  (experiments 
Nos.  1-3)  - — . 

Milk  (experiments 
Nos.  4-5 ) 

Butter  i  experiments 
Nos.  1-4) 

Milk  (experiment 
No.6) 

Crackers  (experi- 
ment No.6) 

Crackers  <  e  x  p  e  r  i  - 
ments  Nos.  7-10  > 

Milk  ( experiments 
Nos.  7-9) 

Milk  (experiment 
No.10).. 


Per  ct.    Per  ct.  Per  ct. 
9.32     1.610       10.06 


86. 51       . 
86.74  i    . 
9.11 

ffi  .  Ms 

10.81     1. 
7.31     1. 
86.  73 
86. 50       . 


535 

3.34 

542 

3.39 

180 

1.13 

4!C) 

3.09 

820 

11.38 

680 

10.50 

506 

3.16 

Per  ct. 
6.21 

4.42 

4.26 

86. 97 

4.26 

6.18 

6.  4!) 

„: 

4.53 


Per 

72. 

4. 
4. 

4. 
7i). 
73. 

4. 


ct. 
32 

Per  ct. 
2.09 

98 

.  75 

86 

.  75 

... 

•.'.  79 

90 

.67 

39 

1.84 

38 

2. 32 

81 

.73 

01 

.70 

Cats. 
4.221 

.767 

.778 

B.010 

.780 
4.172 
4.301 

.795 


Per  ct. 
0.130 


Phos- 
pho- 
rus. 


Per  ct. 

0. 110 


.036 

.  042 


.034 
.143 
.130 
.034 


.115 
.109 

.094 


ajonr.  Aiuer.  Chem.  Soc.  24  (1902),  p.  1100. 


19 

COMPOSITION  OF  FECES. 

As  slated  above,  the  feces  were  analyzed  by  the  same  methods  as 
the  food  materials.  The  composition  of  the  feces  from  the  various 
experiments  here  reported  is  show  n  in  Table  2,  the  results  being  given 
on  the  water-free  basis,  since  the  amounl  of  water  in  the  fresh  feces 
lias  no  bearing  on  the  questions  here  studied. 

Table  2. — Composition  of  feces. 


u 

=  z. 

si 


p 


(Mid 

661 
662 
663 

r,ti, 
665 
666 
667 

668 

669 


Feces. 


Experiment  No.  1 . 
Experiment  No.  2 . 
Experiment  No.  3  - 
Experiment  No.  4 . 
Experiment  No.  5 . 
Experiment  No.  (>. 
Experiment  No.  7 . 
Experiment  No.  8 
Experiment  No.  9 .. 
i  Experiment  No.  10 


Total 

amount. 

>. 

f 

a-d 

<S 

.Z  I 

•-. 

* 

Oh 

- 

ea 

Gms. 

Gms. 

4 

97.5 

95. 1 

4 

102.1 

99.1 

4 

99. 4 

95.0 

:: 

73. 5 

71).  4 

4 

128.0  133.5 

4 

39.0    37.2 

•r) 

80.0     77.0 

5 

200.0  188.6 

•") 

82. 1     77.  7 

3 

104.2 

100.3 

Per 

CI    III 

97.51 
97.00 
95. 57 
95.  74 
96. 48 
95.29 
96. 32 
94.29 
94.64 
96. 25 


Per 

cent. 
3.12 
2. 72 
2. 93 
4.  L9 
2. 82 
2.  M 
2.94 
2. 75 
2.  77 
3.14 


Per 
cent. 
L9.50 

17. (HI 

18.31 

2(5. 19 
17.63 

17.75 
18.38 
17.18 
17. 31 
19.  (52 


Per 
cent. 
13.63 


Per 
cent. 

38.28 


L6.69  36.70 

16.01  35.92 

21.37  30.46 

9.78  38.91 

L0.75  40.08 

12.24  39.67 

16.94  36.36 

LI.  59  40.02 

10. 48i  37. 79 


Per 
cent. 
28. 59 
29.61 
29. 76 
21.98 
33. 68 
31.42 
29.71 
29. 52 
31.  OS 
32. 11 


Calo- 
rics. 

5.  CHi 

5.  696 
5. 468 
6.043 

5.145 
5.514 
5.574 
5. 782 
5. 503 
5. 271 


Per 
cent. 
0.268 
.246 
.272 
.385 
.270 
.  246 
.  253 
.229 
.2:38 


Per 

cent. 

3. 26 
2.96 
3.26 

1 .  86 
3.56 

3. 97 

3.  s.S 

:i.77 
3.22 
4.11 


EXPERIMENTS   ON   THE    DIGESTIBILITY   OF   BREAD  AND   MILK. 
GENERAL  DESCRIPTION  OF  EXPERIMENTS. 


The  experiments  here  reported  were  made  during  the  years  1900  and 
1901.  The  subject  was  a  healthy  young  man  (the  writer)  with  good 
appetite  and  apparently  normal  digestion  and  nutrition.  The  meals 
were  taken  in  the  laboratory,  sometimes  in  the  company  of  other 
young  men  engaged  in  similar  experiments  and  sometimes  alone.  In 
each  case  (with  a  single  unimportant  exception,  noted  below)  the  diet 
was  decided  upon  in  advance,  and  was  maintained  uniform  through- 
out the  experiment  or  series  of  experiments.  Exactly  one- third  of  the 
day's  ration  was  taken  at  each  meal,  and  the  meals  were  taken  at 
nearly  uniform  hours:  In  the  series  of  1900,  at  6.30 a.  m.,  12.30  p.  m., 
and  6.30  p.  m. ;  in  that  of  1901,  at  7.30  a.  m.,  1  p.  m.  and  0.30  p.  m. 
Excepting  the  butter,  which  was  prepared  in  advance  in  weighed  por- 
tions, the  food  required  for  each  meal  was  weighed  by  the  subject 
when  used. 

Dining  the  time  covered  by  the  experiments  the  subject  was 
engaged  partly  in  the  analytical  and  other  laboratory  work  connected 
with  the  investigation  and  partly  in  preparing  for  publication  the 
results  of  previous  studies.  Little  exercise  was  taken  aside  from  that 
involved  in  the  laboratory  work,  which  was  somewhat  exacting. 


20 

Several  of  the  experiments  were  arranged  in  series,  and  followed 
each  other  without  intermission.  In  other  cases  the  food  taken  on 
the  day  preceding  the  beginning  of  the  experimenl  was  practically  the 
same  as  during  the  experimental  period.  Kadi  experimental  period 
began  with  breakfast,  and  the  Lampblack  used  to  facilitate  the  sepa- 
ration of  the  feces  was  taken  with  this  meal  instead  of  with  the  pre- 
ceding supper.  In  our  experience  it  is  very  much  easier  to  determine 
the  point  which  marks  the  first  appearance  of  the  feces  from  a  meal 
with  which  lampblack  was  taken  than  to  decide  exactly  where  the 
feces  from  such  a  meal  end ;  apparently  because,  as  would  be  expected, 
enough  lampblack  may  sometimes  adhere  to  the  walls  of  the  intestines 
to  give  more  or  less  color  to  the  feces  from  meals  subsequent  to  that 
with  which  it  was  taken.  It  seems,  therefore,  decidedly  preferable  to 
take  the  lampblack  with  the  first  meal  of  the  period  and  the  first  meal 
following  the  period,  so  that  the  point  of  separation  shall  be  in  each 
case  the  point  at  whieh  the  lampblack  first  appears  in  the  feces.  In 
each  of  the  digestion  experiments  the  urine  was  collected,  beginning 
with  the  time  at  which  the  first  breakfast  was  taken,  and  the  nitrogen, 
sulphur,  phosphorus,  and  heat  of  combustion  determined. 

The  details  of  the  digestion  experiments  are  included  in  the  follow- 
ing tables.  These  show  the  kind  and  amount  of  food  eaten  by  the 
subject  and  the  weight  of  the  subject  at  the  beginning  and  end  of  the 
experiment.  The  amount  of  protein,  fat,  and  carbohydrates  in  each 
food  material  and  in  the  feces  was  computed  from  the  weight  of  each 
material  multiplied  by  its  percentage  composition  as  shown  in  Tables 
1  and  2.  The  heats  of  combustion,  shown  in  the  last  column  of  the 
tables,  were  determined  by  burning  the  material  in  the  bomb  calorim- 
eter and  multiplying  the  total  weight  of  food  or  feces  by  the  heat  of 
combustion  of  1  gram,  as  thus  determined.  The  differences  between 
the  total  nutrients  in  the  food  eaten  and  those  rejected  in  the  feces 
are  taken  as  a  measure  of  the  total  amounts  digested,  although  of 
course  the  feces  do  not  consist  entirely  of  undigested  residues,  but 
contain  a  relatively  large  amount  of  metabolic  products."  The 
amounts  of  nutrients  rejected  in  the  feces,  while  not  strictly  repre- 
senting the  undigested  portion  of  the  food,  do  represent  approximately 
the  amounts  which  are  not  available  to  the  bod}'.  The  total  amount 
of  any  particular  kind  of  nutrient  digested  or  available  divided  by  the 
total  amount  of  this  nutrient  in  the  food  gives  the  percentage  which 
is.  digestible  or  actually  available  to  the  body.  These  percentage 
values  are  called  coefficients  of  digestibility  or  availability. 

While  the  coefficients  of  digestibility  of  the  different  nutrients  rep- 
resent the  proportion  which  the  body  actually  utilizes,  the  correspond- 
ing value  for  the  heat  combustion  of  the  food  does  not  represent  the 

«See  discussion  of  this  subject  in  Connecticut  Storrs  Sta.  Rpts.  1896,  p.  166,  and 
1897,  p.  156. 


, 


21 

actual  amount  of  energy  which  the  body  obtains  from  the  food  absorbed 
from  the  alimentary  canal.  When  protein  is  burned  in  the  bomb 
calorimeter,  the  carbon  Is  oxidized  to  carbon  dioxid  and  the  hydrogen 
to  water,  the  nitrogen  being  reduced  to  the  free  state.  When  protein 
is  burned  in  the  body,  however,  the  oxidation  isnol  so  complete.  The 
nitrogen  is  excreted  in  the  form  of  urea,  uric  acid,  and  othei  com- 
pounds, which  also  contain  small  amounts  of  carbon  and  hydrogen, 
together  with  some  oxygen.  In  estimating  the  actual  fuel  values  of 
the  digestible  nutrients  of  the  food,  allowance  musl  be  made  for  these 
incompletely  oxjdized  residual  products  which  arc  excreted  by  the 
kidneys.  Urea  is  the  most  abundant  of  these  excretory  products,  and 
it  lias  frequently  been  assumed  that  all  of  the  nitrogen  excreted  in  the 
urine  is  thus  combined,  and  allowance  is  made  for  the  heat  of  com- 
bustion of  the  amount  of  urea  corresponding  to  the  amount  of  nitrogen 
found  in  the  urine.  According  to  this  last  supposition,  0.87  calorie 
of  the  energy  latent  in  each  gram  of  digestible  protein  would  be  Lost 
to  the  body  in  the  urea  formed  from  the  nitrogen  of  the  protein."  In 
a  considerable  number  of  actual  determinations  of  the  ratio  of  the 
nitrogen  to  heat  of  combustion  in  urine  of  healthy  men  made  by 
At  water  and  associates  at  Middletown,  Conn.,  tin4  average  heat  of 
combustion  of  the  organic  matter  in  the  urine  corresponding  to  1  gram 
of  digestible  protein  amounts  to  1.25  calories.  In  the  experiments 
here  reported  the  actual  heat  of  combustion  was  determined  in  each 
instance  The  average  of  these  determinations  corresponded  to  1.20 
calories  per  gram  of  digestible  protein. 

The  results  of  the  individual  tests  are  given  below.  Following  the 
tabular  statement  of  the  details  of  each  experiment  is  a  paragraph 
showing  the  nitrogen  balance;  that  is,  whether  the  subject  gained  or 
lost  nitrogen  during  the  test.  The  discussion  of  the  nitrogen  balance, 
as  well  as  that  of  sulphur  and  phosphorus,  will  be  found  in  another 
section  of  this  report  (pp.  31-46). 

DIGESTION  EXPERIMENT  NO.    1. 

This  experiment  began  with  breakfast  July  20,  1900,  and  continued 
four  days.  The  weight  of  the  subject  (without  clothing)  at  the  begin- 
ning was  60.1  kilograms,  at  the  end  GO  kilograms. 

a Urea  contains  46.67  per  cent  nitrogen  and  has  a  heat  of  combustion  of  2.54 
calories  per  gram.  One  gram  of  protein  (16  per  cent  nitrogen)  would  yield 
(16^-46.6;  =  )  0.342  gram  urea  with  a  heat  of  combustion  of  (2.54X0.342=)  0.87. 
See  also  U.  S.  Dept.  Agr.,  Office  of  Experiment  Stations  Bui.  53,  pp.  27  and  38. 


22 


Table  3. — Results  of  digestion  experiment  No.  1  {serial  No.  324). 


0  Pi 

II 

Kind  of  food. 

ei 

i 
s 

!  * 

- 

= 
i    . 

-  - 

-a 

.- 

X 

I 

- 

Fat. 

i 

\ 
\ 

< 

- 
- 

lirui  of  oombtu 
t  Ion    (deter- 
mined). 

651  I 

Crackers 

linn, is. 

1,200 

8,160 
100 

Grams. 

1,063.0 

1,039.5 

140. 9 

Grams. 
120.7 

1.8 

(ndiits. 

360.6 
130.1 

Grams. 
406.4 

Grams. 

25. 1 

61 . 2 
4.5 

(niiins. 

19.32 

4:5. 66 

.29 

Coteries. 

5  065 

851 
658 

Milk... 

Butter 

Total 

Feces  (water  fine 
Amount  digested 

1  282 



2.24:3.4 

395 

574.2 

1.274.2 

a  i.  - 

63.27 

12,605 

600 

95.1 

67.9 
2,175.5 

97.0 

18.5 
376.  S 
95.3 

13 
561.2 

97.7 

36.4 

1,237.8 

97.2 

27.2 
63.6 
70 

2.97 
60.30 
95.3 

57.23 

541 

12  t*'A 

Per  cent  digested 

Nitrogen  and  heat  of 
combustion  of  urine 

Energy  of  food   oxi- 
dized in  the  body... 

434 

11.630 

Per  cent   of  energy 
utilized 

92.3 

During  this  experiment  the  subject  eliminated  2,550  grams  of  urine, 
containing  57.23  grams  of  nitrogen.  The  average  balance  per  day 
was  therefore:  Income  in  food,  15.82  grams;  outgo  in  urine,  14.31 
grams,  and  in  feces,  0.74  gram;  implying  a  gain  to  the  body  of  0.77 
gram  of  nitrogen,  corresponding  to  4.81  grams  of  protein. 

DIGESTION  EXPERIMENT  NO.  2. 

This  experiment  began  with  breakfast  July  :?4, 1900,  and  continued 
four  days.  The  weight  of  the  subject  (without  clothing)  at  the  begin- 
ning was  60  kilograms,  at  the  end  61  kilograms. 

Table  4. — Results  of  digestion  experiment  Xo.  2  (serial  No.  325). 


Kind  of  food. 

i 

I 

Total  organic 
matter. 

Protein  (Nx  6.25). 

Pat. 

1 
g 

>> 

I 

- 

4 

< 

c 
? 

1 

z 

Heat  of  combus 
t  ion  ( d  0 1  e  r  - 
mined). 

650  Crackers 

651  Milk. 

653     Butter... 

Grains. 

1,200 

8.160 

160 

Grams. 

1.063.0 

1,039.5 

140.9 

Grams. 
120. 7 

272. 5 
1.8 

Grains. 

74.:> 

360.6 

139.1 

Grams. 
867.8 
406.4 

Grains. 

25.1 

61.2 

4.5 

Grams. 
19.32 

43.66 
.29 

Calories. 
5,066 
fi.  256 
1,282 

Total 



2.243.4 

395 

574.2 

1.274.2 

90.8 

63.27 

12.605 

661 

Feces  (water free > 

99.1 

69.7 

2.173.7 

96.9 

16.8 
95.8 

16.5 
557.  7 
97.1 

36.4 

1.237.8 
97.2 

29.3 
61.5 

2.70 
60.57 
95.8 

58.69 

564 
12,041 

95.5 

Nitrogen  and  beat  of 

combustion  of  urine 

Energy  of  food  oxi- 

438 

11,603 

Per  cent  of   energy 

92.3 

28 

During  this  experiment  thesubjecl  eliminated  3,451  grams  of  urine, 
containing  58.69  grams  of  nil  rogen.  This  makes  i  be  average  ail  rogen 
balance  per  day  as  follows :  Income  in  food.  L5.82  grams;  outgo  in 
urine,  L4. 67  grams,  and  in  feces,  0.67  gram;  indicating  a  gain  to  the 
body  of  0.48  gram  of  nitrogen,  corresponding  fco  3  grams  of  protein. 

DIGESTION  EXPERIMENT  NO.   3. 

This  experiment  began  with  breakfast  July  28,  L 900,  and  continued 
four  days.  The  weight  of  the  subject  (without  clothing)  at  the  begin- 
ning was  ill  kilograms,  at  the  end  60.9  kilograms. 


Table  5. — Results  of  digestion  experiment  No.  S  (serial  No. 


a  Pi 

>.= 
it 

Kind  of  food. 

& 

a 

.a 
'5 

Total  organic 
matter. 

Protein(Nx6.25). 

-t-> 

CO 

9 

o 

3 

i 

525 

jr.  ■' 

o  =  -: 

-.£■= 
;  -  - 
H 

650 
651 
653 

Crackers 

Grq,ms. 
1,200 

lint  ins. 
1.063.0 

Grams. 
120.7 
872.5 

1.8 

Grams. 

74.  5 

360.6 

139.1 

Grams. 
867.8 

406.4 

Grams. 

25.1 

61.2 

4.5 

Grams. 

19.32 

43.66 

.29 

Calories. 
5,065 

Milk.. 

8,160     1,039.5 
160        140.9 

6,258 

Butter 

Total 

1,282 

2,243.4 

395 

574.2 

1,274.2 

90.8 

63.27 

12,605 

662 

Feces  (water  free)  ... 
Amount  digested 

95 

66.7 
2,176.7 
97 

17.4 
377.6 
95.6 

15.2 
559 
97.4 

34.1 

1.240.1 

97.3 

28.3 
62.5 
68.8 

2.78 
60.49 
95.60 

56.65 

519 

12,086 

95.9 

Nitrogen  and  heat  of 

combustion  of  urine 

Energy  of  food  oxi- 

435 

11.651 

Per  cent  of   energy 
utilized 

92. 4 

During  this  experiment  the  subject  eliminated  4,071  grams  of  urine, 
containing  5(5.65  grams  of  nitrogen.  This  makes  the  average  nitro- 
gen balance  per  day  as  follows:  Income  of  food,  15.82  grams;  outgo 
in  urine,  14.16  grams,  and  in  feces,  0.70  gram,  indicating  a  gain  of 
0.96  gram  of  nitrogen  or  6  grams  of  protein. 

DIGESTION  EXPERIMENT  NO.   4. 


This  experiment  began  with  breakfast  August  11,  1900,  and  con- 
tinued four  days.  The  weight  of  the  subject  (without  clothing)  at  the 
beginning  was  60.6  kilograms,  at  the  end  62  kilograms. 


'24 


Table  6. — Results  of  di  serial  No. 


>.  0 
t  '- 

- 

Kind  of  food. 

~- 

1 

•-- 
-  - 

1 

Fat 

> 

Ajfa 

\  11 ro 

-  -. 
?- 

■-    - 

-  -  . 

-  -  = 
- 

mn 

4,000 

240 

Gin  1, is. 

500.4 
211.4 

ms. 
163.0 
135. 6 

170.4 

Grams. 

1,171.5 

194.  4 

30 

lira  ins. 

■ 

1  Milk  .. 

Butter 

-    water  fri 

Amount  diLr'-sTed.  — 

Per  cent  digested 

Nitrogen  and  heat  of 
combustion  <  >f  urine 

Energy  of  food  oxi- 
dized in  the  bodv . . . 

3,112 

1 .  922 



»1, 610.2 

226 

1,024.4 

53 

70.6 

36.14 

S.9IU 

66:3 

70.4 

41.2 

B 

11.3 
96.9 

16.1 

11.6 
41.4 

2.21 

319 

M  4 



Per  cent   of   em 
utilized 

■ 

a  Three-fourths  of  total  amount:  urine  for  first  day  lost. 


The  urine  for  the  first  day  of  this  experiment  was  lost.     During  the 

remaining  three  days  the  subject  eliminated  1,990  grams  of  urine, 
containing  31.28  grams  of  nitrogen.     This  makes  the  average  niti    \ 
balance  per  day  as  follows:  Income  in  food.  12.05  grams;  outgo  in 
urine.  10.43  grams,  and  in  feces.  0.74  gram:  indicating  that  the  body 
gained  0.88  gram  of  nitrogen,  or  5.50  grams  of  protein  per  day. 

DIGESTION  EXPERIMENT  NO    5. 

This  experiment  began  with  breakfast  August  15,  1900,  and  con- 
tinned  four  days.  The  weight  of  the  Bubject  (without  clothing)  at  the 
beginning  was  62  kilograms,  at  the  end  60.8  kilograms. 

Table  ?. — Results  of  digestion  experiment  No.  5  (serial  N 


150 


Kind  of  food. 


Crackers 

Milk  

- 
12,240 

Grams. 

425.  8 

1,531.2 

415 

■ 
52L4 

Grams. 
347.1 
594.8 

Grams. 
10 

- 

66.34 

2,026 

9. 523 

Total.. 

1,966.4 

463. 3 

551.2 

£41.9 

101.8 

74. 07 

11.549 

Feces  i  water  free  > 

Amount  digested 

Per  cent  digested 

123. 5 

81.9 
1,874.5 

21.8 

441.5 

95. 3 

12.1 
539.1 

97.8 

48 

41.6 
60.2 
59.1 

3.48 

95.3 
66.01 

635 

in. 914 
94.5 

Xitrogen  and  heat  of 
combustion  of  urine 

4-7 

Energy  of  food  oxi- 
dized in  the  bodv. . . 

10.427 

Per  cent  of    energy 
utilized «... 

90.3 

1 

25 


During  this  experiment  the  subject  eliminated  7,8$9  grams  of  urine, 
containing  66.01  grams  of  nitrogen,  making  the  average  nitrogen  bal- 
ance per  day  as  follows:  [ncome  in  food.  L8. 52  grams;  outgo  in  urine, 
L6.50  grams,  and  in  feces,  u.v7  gram;  implying  a  gain  of  L.  15  grams 


of  nitrogen  or  7.19 


if  protein. 


DIGESTION  EXPERIMENT  NO.  6. 

This  experiment  began  with  breakfast  July  l.  L901,  and  continued 
fourdays.  Theweighl  ofthesubject  i  without  clothing)  al  the  begin- 
ning was  61.45  kilograms,  at  the  end  60.13  kilograms. 

Tabu:  8. — Results  of  digestion  experiment  No.  G  (serial  No. 


5  <E 

=  - 

J:  Z 

Kind  of  food. 

I 

■a 

i 

= 

^   . 
i  - 
:  | 

*- 

0 

Protein  i  X    6.26). 

— 
- 

g 

2 

< 

z 

o 

e 

- 

x  I. 

5  - 

Z   - 

■*-  -  .~ 
-J-  z 

X 

865 

( 'r;i<-kers 

Milk 

Total 

Grams. 

480 
6,120 

Grams. 

422.  2 
749.6 

Grams. 

:>4.  t; 
1*9.1 

Grams. 

29.  7 
260.  7 

Grams. 

337.  it 
299. 8 

Grams. 

8.8 

41 

Grams. 
30.28 

Calories. 

4.774 

1,171.8 

24a : 

*W  4 

637.7 

49.8 

39.03 

♦5.777 

-    water  free )  . . . 
Amount  digested 

37.2 

25.5 
1,146.3 

6.6 
237.1 

97.3 

14.9 

11.7 
38.1 

1.06 
37.97 

97.  3 

43177 

205 

Per  cent  digested 

'.17 

Nitrogen  and  heat  of 
combustion  of  urine . 

Energv  of  food  oxi- 
dized in  the  body  . . . 

350 

6.222 

Per  cent  of   energy 
utilized- 

91.8 

• 

During  this  experiment  the  subject  eliminated  3,232  grams  of  urine, 
containing  43.77  grams  of  nitrogen.  The  average  nitrogen  balance 
pci- day  was  therefore:  Income  in  food,  9.76  grams;  outgo  in  urine, 
10.94  grams,  and  in  feces,  0.27  gram;  indicating  a  loss  of  1.45  grains 
of  nitrogen  or  9.0(3  grams  of  protein. 

DIGESTION  EXPERIMENT  NO.  7. 


This  experiment  began  with  breakfast  July  14,  1001,  and  continued 
five  days.  The  weight  of  the  subject  (without  clothing)  at  the  begin- 
ning was  60  kilograms,  at  the  end  59.2  kilograms. 


26 


T\r.i'.K  9. — Results  of  digestion  experiment  No.  :  {serial  No.  330), 


u 

a  ~ 
-  - 

So 

• 
Kind  of  food. 

1 

r 

s 

is 

- 

"2 

boh 

~  - 

oS  S 

Protein  I  N     6.86). 

i 
- 

I 

6 

4 

< 

l  ■- 
1% 

3  fl  a 

«—  3 
i  _  - 

w 

Rftfi 

Crackers... 

Grams. 
750 

7,500 

Grams. 

077. 8 
940.4 

lira  ins. 

■>s.± 

237 

(iriinis. 

4*.  7 

342. 7 

Grams. 
550.3 
360.7 

Grams. 

17.  4 
54.7 

Grams. 
12.60 
37.96 

Calories. 

3,226 

r,:,; 

Milk 

5.9ii3 

Total.. 



l.tils.:.' 

315. 8 

381.4 

911 

72. 1 

50.55 

9.189 

666 

Feces  (water  free)  ... 
Amount  digested 

77 

54.  1 

1,554.1 

96.7 

14.2 

301.6 

95.5 

9.4 
388 

97.6 

30.5 

880.5 

96.7 

22.9 
49.2 
68.2 

2.26 
48. 28 
95.5 

:,;  58 

429 
8,760 
95  3 

Nitrogen  and  heat  of 

combustion  of  urine 

Energy  of  food  oxi- 

460 

8,300 
90.3 

Per  cent  of    energy 
utilized 

During  this  experiment  the  subject  eliminated  3,027  grams  of  urine, 
containing  57.53  grams  of  nitrogen.  This  makes  the  average  daily 
nitrogen  balance  as  follows:  Income  in  food,  10.11  grams;  outgo  in 
urine,  11.51  grams,  and  in  feces,  0.45  gram;  corresponding  to  a  daily 
loss  of  1.85  grams  of  nitrogen  or  11.56  grams  of  protein. 


DIGESTION  EXPERIMENT  NO.  8. 

This  experiment  began  with  breakfast  July  19,  1901,  and  continued 
five  days.  The  weight  of  the  subject  (without  clothing)  at  the  begin- 
ning was  59.2  kilograms,  at  the  end  60.7  kilograms. 

Table  10. — Results  of  digestion  experiment  No.  S  (serial  No.  331). 


Is 

a  & 

.f  z 

Kind  of  food. 

-p 

1 

■o 

8. 

n 

°^ 
si 

■*= 

0 

CO 

X 

$ 

1 

-t-> 

B 

g 
•a 

>> 

■s 
■s 

8 

4 

< 

1 

Heat  of  combus- 
tion    (deter- 
mined). 

656 

Crackers 

Grams. 

1,500 

15, 000 

Grams. 
1.355. 5 
1,881 

Grams. 
157.5 
474 

Grams. 

97.3 
685.5 

Grams. 

1.100.7 

721.5 

Grams. 
34.8 

109.5 

Grams. 
25.20 
75.90 

Calories. 
6,452 

657 

Milk 

11,925 

Total 

3,236.5 

631.5 

782.8 

1,822.2 

144.3 

101. 10 

18. 377 

Feces  ( water  free) 

Amount  digested 

667 

188.6 

132.9 

3,103.6 

95.9 

32.4 

599.1 

94.9 

31.9 
750.9 
95.9 

68.6 

1.753.6 

96.2 

55.7 
88.6 
61.4 

5.19 
95.91 
94.9 

77.62 

1,090 
17,287 

Per  cent  digested 

94.1 

Nitrogen  and  heat  of 

606 

Energy  of  food  oxi- 

16,681 

Per  cent  of  energy 

90.8 

1 

27 

During  this  experiment,  which  followed  No.  7  without  intermission, 
the  subject  eliminated  5,223  grams  of  urine  containing  77.62  grams  of 
nitrogen.  This  makes  the  average  uitrogeu  balance  per  day  as  fol- 
lows: Income  in  food,  20.22  grams;  outgo  in  urine,  L5.52  grams,  and 
in  feces,  L.04  grams;  implying  a  storage  in  the  body  of  3.66  grams  of 
uitrogen,  corresponding  t<>  22.87  grams  of  protein. 

DIGESTION  EXPERIMENT  NO.   9. 

This  experiment  began  with  breakfast  July  24,  L901,  and  continued 
five  days.  The  weight  of  the  subject  (without  clothing)  at  the  begin- 
ning was  GO. 7  kilograms,  at  the  end  50.3  kilograms. 


Table  11. — Results  of  digestion  experiment  No.  i)  {serial  No. 


k 

Kind  of  food. 

1 

a 

"2 

e3     . 

H 

CO 

o 
Eh 

«e 

X 

g 

o 
u 

1 

08 

>, 
A 

0 

1 

o 

4 
< 

a 

a> 
be 

o 

Heat  of  combus- 
tion (deter- 
mined). 

656 
657 

668 

Grams. 

750 

7,500 

Grams. 

677.8 
940.4 

Grams. 

78.8 
237.0 

Grams. 

48.7 

342.7 

Grams. 
550.3 
360.7 

Grams. 
17.4 
54.7 

drains. 

12.60 
37.95 

Calories. 

3.226 

Milk 

5.963 

Total 

1,618.2 

315.8 

391.4 

911.0 

721 

50.55 

9,189 

Feces  (water  free) 

Amount  digested 

77.7 

53.6 

1,564.6 

96.7 

13.5 

302.3 

95.7 

9.0 
382.4 
97.7 

31.1 
879.9 
96.6 

24.1 
48.0 
66.6 

2.15 
48.40 
95.7 

64.33 

428 
8,761 

Per  cent  digested 

95.3 

Nitrogen  and  heat  of 

479 

Energy  of  food  oxi- 
dized in  the  body 

8,282 

Per   cent  of  energy 
utilized 

90.1 

During  this  experiment,  which  followed  No.  8  without  intermission 
and  which  was  a  duplicate  of  No.  7,  the  subject  eliminated  4,310 
grams  of  urine  containing  64.33  grams  of  nitrogen.  The  average 
daity  nitrogen  balance  was  therefore:  Income  in  food,  10.11  grams: 
outgo  in  urine,  12.87  grams,  and  in  feces,  0.43  gram;  indicating  a  loss 
of  3.19  grams  of  nitrogen,  or  19.94  grams  of  protein. 

DIGESTION  EXPERIMENT  NO.  10. 


This  experiment  began  with  breakfast  July  29,  1901,  and  continued 
three  days.  The  weight  of  the  subject  (without  clothing)  at  the  begin- 
ning was  59.3  kilograms,  at  the  end  60  kilograms. 


28 


Table  12.-  -Results  of  digestion  experiment  No.  10  (serial  No. 


U 

a  p. 
fa 


666 
658 


669 


Kind  of  fo 

Weight  of  mate- 
rial. 

- 
- 

~- 

0 

I 
z 
u 
0* 

1 

g 

>> 

1 

■a 

< 

2sh 

2© 

9  © 

•-    - 

-  -  ■- 

-  -  = 

s  —  - 

W 

Crackers 

Milk  

Crams. 

900 
9,000 

Grams. 

813.3 

1,152.0 

(.rums. 

94.5 
293.  4 

Grams. 

58.  1 
407.7 

C ra  ins. 

660.4 
450.9 

Grams. 
63.0 

Grams. 
L5.  L2 
16. 98 

Calorics. 

3,871 
7,020 

Total... 



387. 9 

466.1 

1,111.3 

83.9 

62.10 

10.891 

Feces  I  water  Prei 

Amount  digested 

100.3 

68.1 

1,897.2 

96.5 

19.7 
94.9 

10.5 
455.  6 

37.9 

1,073.4 

96.  6 

32.  2 
51.7 
61.6 

3. 15 
58.95 
94.9 

-tit.  74 

529 
10.362 

Per  cent  digested 

95.2 

Nitrogen  and  heat  of 
combustion  of  urine 

374 

Energy  of  food  oxi- 
dized in  the  body. . . 

9,988 

Per  cent   of  energy 
utilized  _ 

91.7 

This  experiment  followed  No.  9  without  intermission.  The  diet 
was  nearly  the  same  as  in  Xo.  8.  During  the  three  days  of  this  experi- 
ment the  subject  eliminated  4,290  grams  of  urine  containing  49.74 
grams  of  nitrogen.  The  average  nitrogen  balance  per  day  was  there- 
fore: Income  in  food,  20.70  grams;  outgo  in  urine,  1G. 58  grams,  and 


indicating  a  gain   of 


in  feces,  1.05  grams 

corresponding  to  19.19  grams  of  protein 


3.07  grams  of   nitrogen, 


RESULTS  OF  DIGESTION  EXPERIMENTS. 

In  Table  13  are  summarized  the  results  obtained  in  the  various 
experiments  on  the  digestibility  of  the  total  food  eaten.  Although  the 
diet  was  composed  in  each  case  of  bread  (in  the  form  of  soda  crack- 
ers) and  milk,  with  butter  in  some  cases,  the  relative  proportions  of 
these  two  food  materials,  as  well  as  the  quantities  taken,  varied  in 
the  different  experiments,  as  will  be  seen  from  the  details  of  the 
experiments  given  above. 

Table  13. — Coefficients  of  digestibility  of  n  utrients  and  availability  of  energy. 


Ex- 
peri- 
ment 
num- 
ber. 

Kind  of  food. 

Protein. 

Fat. 

Carbo- 
hy- 
drates. 

Ash. 

Energy. 

1 

Percent. 
95.3 
95.8 
95. 6 
93.9 
95.3 
97.3 
95.5 
94.9 
95.7 
94.9 

P<  rcent. 

97.7 
97.1 
97.4 
96.9 
97.8 
98.6 
97.6 
95.9 
97.7 
1*7.7 

Percent. 
97.2 
97.2 
97.3 
98.4 
94.9 
97.7 
96.7 
96.2 
96.6 
96.6 

Percent. 
70. 0 
67.7 

78.1 

59.1 
76.5 
68.2 
61.4 
66.6 
61.6 

Percent. 
92.  3 

2 

...do 

92.3 

3 

do - 

92.  i 

4 

do... 

93.  :> 

5. 

Bread  and  milk 

90.3 

6... 

do 

91.8 

...do    . 

90.3 

8.  .. 

...do 

90.8 

9 

do 

90.1 

10. 

do... 

91.7 

29 

As  explained  above,  the  experiments  were  varied  in  ni<i<-r  to  b1  ady 
the  digestibility  under  different  circnmstances,  so  thai  an  average  of 
the  results  obtained  would  have  little  value  except  as  these  variations 
arc  taken  into  consideration.  It  will  be  noted  that  the  results  of 
experiment  NO.  6  differ  markedly  from  all  the  <>t  hers  in  I  he  Larger  per- 
centage of  the  protein  digested,  the  digestibility  of  the  t'.u  being  also 
increased  bu1  not  to  such  a  marked  degree.  This  result  is  not  due  to 
the  relative  proportions  of  bread  and  milk-  in  the  diet, since  in  this 
respect  the  experiment  is  intermediate  between  experiments  Nos.  5 
and  7.  The  amount  of  protein  taken  in  the  food  was  somewhal  less 
than  in  experiment  No.  7,  and  very  much  less  than  in  experiment  No. 
5.  This  fact  would  of  course  be  favorable  to  the  more  complete  absorp- 
tion of  the  protein,  as  would  also  the  circumstance  that  during  Hie 
week  previous  to  the  test  the  subject  had  eaten  less  food  than  usual. 
These  circnmstances  may  account  for  the  rather  unusual  figures 
obtained  in  this  period,  and  as  the  feces  were  collected,  dried,  and 
weighed  by  the  subject  himself  it  would  seem  improbable  that  any 
serious  loss  could  have  occurred  without  being  detected.  Neverthe- 
less, the  amounts  of  total  dry  matter,  nitrogen,  and  phosphorus  found 
in  the  feces  for  this  period  are  so  small  that  the  results  are  given  with 
some  hesitation,  and  in  comparing  the  determined  and  calculated  fig- 
ures for  digestibility  we  have  averaged  the  experiments  both  with  and 
without  No.  6. 

Table  14  shows  for  each  experiment  and  for  the  average  of  all  the 
experiments :  (1)  The  percentage  of  protein  actually  digested,  as  deter- 
mined; (2)  the  digestibility  as  calculated,  assuming  that  85  per  cent  of 
the  protein  from  cereals  and  97  per  cent  of  the  protein  from  milk  were 
digested,  and  (3)  the  figures  calculated  on  the  assumption  that  90  per 
cent  of  the  protein  of  the  bread  and  97  per  cent  of  the  protein  of  the 
milk  were  digested. 

Table  14. — Coefficients  of  digestibility  of  protein,  calculated  and  determined. 


Results  cal- 

Results cal- 

culated, as- 

culated, as- 

suming that 

suming  that 

Results 
actually 

found. 

85  per  cent 
of  bread  pro- 
tein and  97 

90  per  cent 

of  bread  pro- 
tein and  U7 

per  cent 

per  cent 

of  milk  pro- 

of milk  pro- 

tein were 

tein  were 

digested. 

digested. 

Pera  nt. 

Percent. 

Per  cent . 

Experiment  No.  1 

95.  :< 

93.3 

94.9 

Experiment  No.  2 

95. 8 

93.3 

94.9 

Experiment  No.  3 

95.  ii 

93.3 

94.9 

Experiment  No.  4 

93.9 

90.5 

98. 2 

95  3 

95  8 

96  3 

Experiment  No.  ti 

97.3 

93.9 

95  3 

Experiment  No.  7 

95.5 

94.0 

95. 3 

Experiment  No.  8 

94.9 

94.0 

95.3 

Experiment  No.  9 

95. ; 

94.0 

95  3 

Experiment  No.  10 

94.9 

94.0 

95  3 

Average  of  all 

95.4 

93.6 

95.1 

Average,  omitting  experiment  No.  6 

95.2 

93.6 

95  0 

30 

It  will  be  seen  that  the  digestibility  of  the  protein  of  the  diet,  as  cal- 
ciliated  on  the  assumption  that  85  per  cent  represents  the  digestibility 
of  bread  protein  and  97  per  cent  that  of  milk  protein  are  in  9  out  of  the 
10  cases  noticeably  lower  than  the  results  actually  obtained,  the  aver- 
age being  1.8  or  L.6  percent  lower  than  the  average  actual  value, 
according  as  we  do  or  do  not  include  experiment  No.  6. 

If,  however,  we  assume  that  90  per  cent  of  the  bread  protein  was 
digestible,  and  use  the  same  factor  as  before  (97  per  cent)  for  the  milk, 
we  find  thai  (with  the  exception  of  experiment  No.  6)  the  calculated 
and  determined  values  agree  in  every  instance  within  1  per  cent, 
while  the  averages  agree  within  one-quarter  of  1  per  cent,  a  varia- 
tion which  may  well  be  considered  as  negligible. 

The  factor  90  per  cent  for  the  digestibility  of  the  bread  protein  was 
suggested  !r\T  the  fact  that  this  is  about  the  value  found  for  white 
bread  by  Woods  and  Merrill0  in  an  extended  series  of  experiments 
with  a  number  of  different  subjects,  and  also  in  tests  with  one  of  the 
four  subjects  employed  by  Snyder.* 

As  might  be  expected  from  the  fact  that  fat  is  supplied  in  an  emulsi- 
fied and  readily  available  form  in  milk,  its  digestibility  in  these 
experiments  was  rather  higher  than  is  usually  found.  A  detailed 
comparison,  such  as  that  given  for  the  protein,  is,  however,  impracti- 
cable, (1)  because  of  the  impossibility  of  distinguishing  between  ani- 
mal and  vegetable  fats  in  the  crackers  used,  and  (2)  because  those 
portions  of  the  feces  designated  "fats"  and  "carbohydrates"  really 
consist  largely  of  other  substances. 

During  experiment  No.  2,  in  which  the  diet  was  the  same  as  in 
experiments  Nos.  1  and  3,  there  was  (as  will  be  more  fully  described 
beyond,  p.  35)  a  very  considerable  loss  of  sleep.  This,  however,  does 
not  seem  to  have  had  any  appreciable  effect  upon  the  proportion  of 
either  of  the  nutrients  digested. 

Experiments  Nos.  7,  8,  9,  and  10  throw  some  light  upon  the  digesti- 
bility of  liberal  and  restricted  diets.  These  were  carried  out  in  series, 
and  the  relative  proportions  of  milk  and  bread  were  uniform  through- 
out. The  amount  eaten  per  day  was,  however,  twice  as  great  in 
experiments  Nos.  8  and  10  as  in  experiments  Nos.  7  and  9.  On  the 
smaller  diet  the  percentage  digested  was  slightly  higher.  The  differ- 
ence is  quite  small,  less  than  1  per  cent,  but  as  all  other  experimental 
conditions  Avere  carefully  maintained  uniform,  and  as  the  agreement 
between  the  similar  experiments  is  almost  complete,  it  would  seem 
that  the  better  digestibility  shown  by  experiments  Nos.  7  and  9  over 
experiments  Nos.  8  and  10  must  be  attributed  to  the  fact  that  less 
food  was  taken.  Larger  but  more  variable  differences  have  already 
been  observed  by  Snyder  (loc.  cit.)  in  similar  experiments. 

Experiments  Nos.  7  to  10  were  carried  out  without  intermission,  and 

«U.  S.  Dept.  Agr.,  Office  of  Experiment  Stations  Bui.  85,  p.  32. 
&U.  S.  Dept.  Agr.,  Office  of  Experiment  Stations  Bui.  101,  p.  33. 


31 

covered  a  period  of  eighteen  days.  Experiments  Nbs.  I  bo  3  covered 
similarly  a  period  of  twelve  days.  The  results  obtained  from  these 
experiments  make  ii  evidenl  thai  an  extremely  simple  diet  maybe 
continued  for  a  very  considerable  number  of  days  wi1  hout  necessarily 
diminishing  iis  digestibility. 

COMPARISON  OF  THE  METABOLISM  OF  NITROGEN,  SULPHUR,  AND 

PHOSPHORUS. 

As  has  been  explained,  the  experiments  above  discussed  as  diges- 
tion tests  were  also  designed  to  include  a  study  of  the  comparative 
metabolism  of  nitrogen,  sulphur,  and  phosphorus.  In  each  experi- 
ment the  diet  was  uniform  and  the  urine  for  each  twenty-four  hours 
was  collected  and  examined.  Aliquot  portions  of  each  day's  urine 
were  mixed  to  give  a  composite  sample  representing  the  entire  period. 
Nitrogen  was  determined  in  the  urine  of  each  day,  and  the  results 
were  verified  by  the  analysis  of  the  composite  sample. 

Phosphates  in  the  daily  urines  were  determined  volu metrically  by 
titration  with  standardized  uranium  acetate  solution  in  the  usual 
manner.  The  total  phosphorus  of  the  urine  for  the  whole  i>eriod  was 
determined  as  described  in  the  section  on  analytical  methods,  above. 
It  will  be  seen  from  the  results  as  tabulated  below  that  the  sum  of  the 
figures  obtained  by  titration  of  the  daily  urines  ranges  in  the  different 
experiments  from  95.5  to  98  per  cent  of  the  total  by  the  gravimetric 
method  in  the  composite  for  the  period.  These  variations  are  very 
likely  due  as  much  to  errors  in  the  volumetric  determinations  as  to 
differences  in  the  amount  of  "  organic  "  phosphates  present.  If  the 
methods  and  manipulation  were  free  from  error  the  results  would 
indicate  from  0.02  to  0.05  gram  of  phosphorus  (or  0.04  to  0.12  gram 
P.<,G5)per  day  eliminated  in  forms  not  precipitated  by  uranium.  This 
amount  is  so  small  that  it  appears  quite  sufficient  to  use  the  volumet- 
ric method  when  one  desires  merely  to  follow  the  general  course  of 
the  phosphorus  excretion,  determining  the  total  phosphorus  by  the 
standard  gravimetric  method  in  cases  where  an  accurate  balance  of 
income  and  outgo  is  to  be  determined.  In  this  connection  it  may  be 
noted  that  recent  investigations  by  Ceconi  and  others  a  of  the  so-called 
organic  phosphates  of  the  urine  have  given  quite  variable  results 
and  have  not  tended  to  emphasize  the  importance  of  the  small  amount 
of  phosphorus  thus  combined. 

On  account  of  unavoidable  interruptions  it  was  impossible  in  the 
experiments  carried  out  in  1900  to  determine  sulphur  in  the  urine  of 
each  day.  The  amount  of  total  sulphur  and  of  sulphate  sulphur  was, 
however,  determined  for  each  period.     The  same  determinations  were 

"TVerhandl.  Cong.  Innere  Med.  Rome.  1896;  abs.  in  Jahrb.  Thier.-Chein..  2  7 
(1897).  p.  362.  Jolly,  Compt.  Rend.  Acad.  Sci.  Paris.  127  (1898),  p.  118.  Oertel. 
Ztschr.  Physiol.  Chem.,  26  (1898),  p.  123.     Keller,  Ibid..  29  (1900),  p.  146. 


32 


included  in  experimenl  No.  6.  In  experiments  Nos.  7  to  LO  the  sul- 
phate sulphur  was  determined  for  each  day  and  the  total  sulphur  for 
each  period.  Comparing  fche  "  sulphate  "  and  "total"  sulphur  in  the 
differenl  experiments,  ii  would  appear  thai  from  83.1  to  89.6  percent 
of  ili«'  sulphur  in  the  urine  was  in  the  form  of  sulphates.  The  sulphur 
in  forms  other  than  sulphates — so-called  "neutral"  sulphur — has 
recently  been  studied  by  Reale  and  Velardi,*  Harnack  and  Kleine,* 
FivuihI.  Pel  ry, '  and  doubtless  others,  and  will  probably  repay  fur- 
ther investigation.  In  the  present  experiments,  however,  time  did 
not  permit  of  any  study  of  this  question.  Neither  did  tin- analyses 
include  the  separate  determination  of  the  ethereal  sulphates  which, 
as  the  protein  consumed  came  principally  from  milk,  were  probably 
present  in  less  than  the  usual  proportions.' 

The  final  results  of  the  examinations  of  the  urine  are  brought 
together  in  Table  15,  which  shows  the  data  for  each  experimental 
day.  a->  well  as  the  total  for  each  of  the  ten  periods.  Partial  analyses 
of  the  urine  for  the  four  days  immediately  following  experiment  Xo. 
5  are  also  given. 

Table  15. — Data  of  examination  of  urine  in  experiments  Nos.  1—10. 


Exper- 

Date. 

Total 
amount 
voided. 

Specific 
gravity. 

Nitro- 
gen. 

Sulphur. 

Assul-    T       , 
phates.    10Tal- 

Phosphorus. 

Heat 
of  com- 
bus- 
tion. 

nuni- 
ber. 

By  ti- 
tration. 

Total. 

1. 

1900. 
Julv  20-21. 

Gram*. 
817 
908 
998 

838 

1.0280 
L0270 
1.0260 
1.0280 

Grains. 

15.38 
13.89 

14.  28 
13. 68 

Grams. 

1.30 
1.34 
1.40 

1.41 

Grams. 

Cals. 

Jul v  21-22     ..    

Jul v  22-23 

July  23-21. 

Total 

July  24-85 

July  25-26. 

July  26-27 

July  27-28     



3.550 

57.23 

3. 37        3. 80 

5.  45 

.5.63 

433.8 

2- 

852 
782 
851 
966 

1.0280 
1.0300 
1.0310 
1.0285 

13.96 
14. 04 

15.  63 
15.06 

1.28 
1.34 
1.43 
1.66 

Total 

July  28-29.. 

3. 451 

58.69 

3. 46         3.  86 

5.71 

5.90 

438.2 

3 

1.160 
978 
952 

1.001 

1.0250 
1.0270 
1. 0270 
L0255 

15. 65 
13.67 
13. 51 

13.  82 

1.51 
1.34 
1.26 
1.40 

July  29-80 

July  30-31       

July  31-August  1  . . 

Total 

August  12-13 

August  13-14 

August  14-15 

Total 

August  15-16 

August  16-17 

August  17-1  s 

August  18-19 

Total 

4.(>71 

56.65 

3. 24         3.  74 

5.51 

5.66 

434.7 

4 

609 
711 
670 

1.0325 
1.0806 

1.0305 

10.19 
10.92 
10. 17 

.94 
1.06 
1.02 

85.6 

38  : 

83.4 

1.990 

31.28 

1.85        2.16 

3.02 

3.10 

257.7 

2,180 
2. 130 
1,859 
1,720 

1.0130 
1.0120 
1.0145 
1.0150 

15. 12 
16.07 
16.98 
17.84 

1.48 
1.72 
1.79 
1.78 

110.6 

117.4 

127. 3 

131.8 

7.889 

66.01 

3. 94         4. 48 

6.77 

6.96 

487.1 



aStndii  di  clinica  medica,  Xapoli,  1895;  abs.  in  Arch.  Yerdauungskrankh..  2 
(1896-97).  p.  141. 

eZtschr.  Biol..  37  (1899).  p.  417. 

cZtschr.  Physiol.  Chem.,  29  (1900),  p.  '24. 

dlbid.,  '1\)  (1900),  p.  45. 

e  See  results  by  Laquer.  Yerhandl.  Cong.  Innere  Med..  16  (1898).  p.  546;  abs.  in 
Jahrb.  Their. -Chem.,  28  (1898),  p.  336. 


33 


i  i."».    -Data  of  >  xamination  of 


/  //.  nta  Noa.  t-10— Continued. 


Exper 

Total 

amount 
voided. 

Specific 
gravity. 

Nitro- 
gen. 

Sulphur. 

Phosphorus. 

Heat 
of  com- 

tion. 

ber. 

phates. 

Total. 

By  ti- 
tration. 

Total. 

1900-Contd. 

August  19-20 

August  20  21 

August  21  22  

August  22-28 

Total 

Grants. 
1,698 

1,730 
1 .  ■  15 
1,835 

L.0150 
L.0150 
L.0170 
L.0150 

Grams. 
L8.  L2 

17.78 

Grams. 

Grams. 

L.70 
L.71 

l.i.'.' 

6,808 

72.82         l     , 

6.86 

1 

L901. 
July  4-6 

. 

6 

879 
641 
760 
952 

L0230 

1     275 
L.0270 
L.0215 

! 

LO  58 

.'.Mi 

1.01 
1.10 
L.21 

July  5  6 

in.  !:.' 
L1.32 

J  1.45 

July  6-7 

juiv :  a 

Total . . 

3. 232 

43.77  |      2.57 

3.00 

4. 2*         L.  46        350. 3 

July  14-15  __ 

7 

681 
605 
620 

566 
555 

1.0320 
L.0320 
1.0320 

1.0350 
1.0350 

11.65 
11.12 
11.35 
11.  <v, 
11.75 

.68 

.72 
.68 
.69 

.84 

July  15-16. 

.  99 
1.04 

July  1(5-17... 

July  17-  L8 

July  18-19 

Total 

July  19-20 

July  20-21  ... 

3,027 

57.53 

3.44 

4.14 

4.75        4.98        459.8 

8 

6b7 

874 

1,460 

1,110 
1,092 

1.0340 
1.0310 
1.0200 
1. 0270 
1.0290 

14. 83 
15.81 
15.19 

14.91 
16.88 

.93 
.90 
.89 
.96 

1.04 

1.19 
L.43 
1.42 
1.60 
1.57 



July  21-22 

July  22-23 

July  2:*-24 

Total 

5,223 

77.62 

4.72 

5.28 

7.21         7.44         605.9 

July  24-2-") 

9 

790 

1.0280 
1.0290 
L.0270 
1.0240 

1 . 0260 

12.64 

12.  57 
13. 01 
12.73 

12.88 

.77 
.75 

.79 

.72 
.78 

1 .  25 

July  25-26 

783 
936 
902 
899 

1.21 
1.37 
L.25 

1.21 

July  26-27  .     - 

July  27-28 

July  28-29 

Total 

July  29-30 

4,310 

64.  &3 

3.81 

4.33 

6.29        6.59  |      478.8 

10 

1,340  ;      1.0200 
1,750        1.0200 
1,200         1.0240 

16.23 
16.71 

16.  80 

1.02 
1.05 
1.04 

1.33 

1.44 

1.51 

July  30-81   ..  . 

July  31-August  1  . . 
Total 

4,290 

49.  74 

3.11 

3.64           4.28         4.46         374.1 

With  the  exception  of  experiment  No.  6,  the  experiments  fall  into 
three  series,  as  will  be  seen  from  the  datesgiven  in  the  table.  The  gen- 
eral occupation  and  habits  of  the  subject  were  similar  in  all,  except 
as  modified  for  the  experiment  in  which  the  eifect  of  loss  of  sleep  was 
studied,  and  have  already  been  described.  The  first  series  included 
three  four-da}"  experiments  (Nos.  1.  2,  and  3)  carried  out  in  the  latter 
part  of  July,  1900.  The  bread  and  milk  diet  was  taken  for  a  day  and 
a  half  before  the  beginning  of  the  first  experiment.  The  diet  was 
entirely  uniform  throughout,  except  that  on  the  first  day  60  grams 
and  on  the  second  day  20  grams  of  butter  were  taken,  after  which  40 
grams  per  day  were  taken  throughout.  The  fuel  value  of  the  diet  was 
thus  a  little  above  the  average  on  the  first  and  a  little  below  the  aver- 
age on  the  second  day.  but  was  the  same  for  each  of  the  three  periods, 

9861— No.  121—02 3 


84 

and  except  for  this  slight  variation  in  the  amounl  of  fat  taken  on  the 
first  two  days  the  daily  diet  was  uniform  throughout  the  twelve  days 
covered  by  i  he  series. 

The  second  series,  including  experiments  Nos.  1  and  5,  was  begun  ten 
days  after  the  conclusion  of  the  first  series.  During  most  of  the  inter- 
vening time  the  subject  had  Toll  owed  1h<'  usual  font  i  ue  and  Lived  on  a 
rather  simple  mixed  diet  consisting  Largely  oi  bread,  milk,  and  fruit. 
Three  days  short  ly  before  t  he  beginning  of  experiment  No.  4  (August  7 
to  9  inclusive)  were,  however,  spent  in  another  place  and  under  some- 
what different  conditions,  the  work  being  more  active  and  the  diet 
more  abundant  and  varied,  and  consisting  more  Largely  of  meat. 
Experiment  Ho.  4  was  really  begun  on  the  morning  of  August  11,  and 
the  feces  collected  correspond  to  a  period  of  four  days.  Unfortu- 
nately the  urine  of  the  first  day  was  Lost,  so  that  as  a  metabolism 
experiment  it  covers  only  three  days  preceded  by  a  day  in  which 
exactly  the  same  diet  was  taken.  In  calculating  the  balance  of  income 
and  outgo  for  the  three  days  it  is  assumed  that  the  elimination  of  feces 
was  practically  uniform.  As  compared  with  the  preceding  experi- 
ments the  diet  in  experiment  Xo.  4  was  about  normal  as  regards  fuel 
value  but  low  in  protein.  While  this  diet  was  evidently  sufficient  for 
the  needs  of  the  body,  the  large  amount  of  bread  and  butter  was  not 
appetizing  to  the  subject,  who  during  this  experiment  felt  a  little  less 
vigorous  than  usual,  though  perfectly  well.  After  four  days  on  this 
diet  experiment  No.  5  was  begun,  the  diet  being  changed  by  omitting 
the  butter,  reducing  the  bread  to  less  than  one-third  and  greatly 
increasing  the  amount  of  milk,  so  that  the  diet  had  nearly  the  same 
fuel  value  as  in  experiment  No.  4,  but  furnished  over  50  per  cent 
more  protein. 

In  the  third  series  (experiments  Nos.  7  to  10)  carried  out  in  July, 
1901,  the  diet  was  qualitative!}7  uniform  throughout  the  eighteen  days 
covered^that  is,  the  diet  consisted  of  bread  and  milk  in  the  same 
relative  proportions.  The  amounts  taken  daily  were,  however,  twice 
as  great  in  experiments  Xos.  8  and  10  as  in  experiments  Nos.  7  and 
9.  The  daily  routine  was  similar  to  that  followed  in  the  preceding- 
experiments,  except  that  the  experimental  day  was  begun  at  7.30 
a.  m.,  instead  of  G.30  a.  m. 

The  results  obtained  can  be  best  discussed  by  considering  sepa- 
rately the  different  points  on  which  the  experiments  were  designed  to 
throw  some  light. 

INFLUENCE  OF  LOSS  OF  SLEEP. 

Roeskea  as  the  result  of  an  extended  study  of  the  course  of  the 
phosphorus  excretion   during  the  day  concluded   that    the  degree  of 


aUeber  den  Verlauf  der  Phosphors;  iuiv-Aussclieiclung  heini  Menschen.     Inaug. 
Diss..  Greifswald,  1897. 


85 

mental  and  vital  activity,  and  especially  the  alternation  of  sleeping 
and  waking  periods,  had  a  greater  influence  upon  the  excretion  of 
phosphorus  than  did  the  food  ingested.  Thus,  when  the  urine  was 
collected  and  the  phosphorus  determined  for  cadi  two-hour  period 
from  the  time  of  rising — 6  a.  m. — till  thai  of  retiring — 11  p.  m. — the 
curve  representing  the  excretion  was^quite  similar  from  day  to  day. 
This  normal  course  of  the  excretion  was  not  greatly  altered  by  chang- 
ing the  diet  or  even  by  omitting  a  meal  entirely,  bu1  was  strikingly 
changed  when  the  subject  rose  two  limns  before  the  usual  lime  in  the 
morning.  The  food  and  feces  were  not  analyzed  and  apparently  the 
did  was  qoI  the  same  on  the  different  " normal "  days,  so  that  the 
conclusions  were  necessarily  based  more  Largely  upon  alterations  in 
the  form  of  the  curve  representing  the  excretion  than  upon  the  total 
amount  excreted  during  the  day,  and  as  neither  nitrogen  nor  sulphur 
was  determined  there  is  nothing  to  indicate  whether  or  not  the 
changes  in  phosphorus  metabolism  accompanied  similar  changes  in 
the  metabolism  of  proteid  material.  In  view  of  1  hose  questions  it 
seemed  desirable  in  beginning  the  present  investigation  to  give  some 
attention  to  this  matter,  in  order  to  ascertain  whether  unusual  pre- 
cautions as  to  regularity  of  hours  would  be  necessary  in  experiments 
in  which  the  metabolism  of  phosphorus  was  to  be  studied  in  com- 
parison with  that  of  nitrogen.  This  point  was  studied  by  greatly 
reducing  the  time  spent  in  sleep  in  experiment  No.  2,  all  of  the  other 
conditions  (which  have  already  been  described)  being  the  same  as  in 
experiments  Nos.  1  and  3.  Experiment  No.  1  ended  and  experiment 
No.  2  began  with  breakfast  of  July  24,  1900.  That  night  the  subject 
slept  but  two  and  one-half  hours,  the  following  night  four  hours,  and 
the  third  night  no  sleep  was  taken.  The  subject  then  returned  to 
his  usual  routine,  sleeping  about  seven  hours  each  day.  The  waking 
hours  of  the  first  night  were  spent  upon  mental  work  of  the  kind  to 
which  the  subject  was  accustomed.  On  the  second  and  third  nights, 
after  the  usual  hour  of  retiring,  the  time  was  passed  in  reading  light 
literature.  Only  on  the  second  night  was  there  difficulty  in  remain- 
ing awake.  Throughout  each  day  and  until  10  or  11  o'clock  in  the 
evening  the  subject  was  engaged  upon  his  usual  duties  and  did  not 
feel  any  distinct  effect  of  the  loss  of  sleep,  except  a  slight  nervousness 
on  the  day  following  the  third  night — that  on  which  no  sleep  was 
taken. 

The  loss  of  sleep  resulted  in  an  increased  elimination  of  each  of  the 
three  elements  studied,  but  as  the  sulphur  was  determined  simply  by 
periods,  onhv  the  nitrogen  and  phosphorus  can  be  compared  in  detail. 
It  will  be  seen  from  Table  15  that  the  increased  elimination  does  not 
appear  until  after  the  second  night  and  then  continues  for  two  days 
after  the  pet  urn  to  the  usual  routine,  thus  running  over  into  the  follow- 
ing period  (experiment  Xo.  3).     The  results  are  best  shown,  therefore, 


36 

qoI  by  a  comparison  of  the  totals  for  the  three  periods,  but  by  aver- 
aging  i  he  days  in  which  the  increase  is  found  actually  to  have  occurred 
and  comparing  with  the  preceding  and  following  days.  Thus  we  find 
for  five  "normal"  days,  beginning  July  21,  an  average  of  13.97  grams 
nitrogen  and  1.355  grams  of  phosphorus,  with  the  following  ratio: 
N  :  P  ::  100  :  9.66.  The  following  three  days,  which  show  the  effect 
of  the  Loss  of  sleep,  average  L5.45  grams  nitrogen  and  1.538  grams 
phosphorus,  with  a  ratio  of  100  :  9.96;  while  the  three  days  next  fol- 
lowing, when  the  elimination  is  again  normal,  average  L3. 67  grams 
nitrogen  and  1.328  grams  phosphorus,  the  ratio  being  100  :  9.65. 

In  view  of  the  amount  of  sleep  lost  the  total  increased  elimination 
seems  quite  small  both  in  the  case  of  nitrogen  and  that  of  phosphorus, 
and  it  is  evident  that  the  latter  was  only  slightly  more  affected  than 
the  former,  since  the  change  in  the  ratio  is  no  larger  than  would  often 
be  found:  on  comparing  successive  "normal"  days  when  all  the  condi- 
tions appear  to  be  uniform. 

The  relative  fluctuations  in  the  amounts  of  nitrogen  and  phosphorus 
eliminated  daily  during  this  series  is  shown  graphically  in  fig.  1,  in 
which  the  solid  line  represents  the  excretion  of  nitrogen  and  the  dot- 
ted line  that  of  phosphorus. 

The  elimination  of  sulphur  as  measured  by  the  four-day  periods  ran 
very  closely  parallel  with  that  of  nitrogen  throughout  this  series,  the 
ratio  N  :  S  being  in  the  first  period  as  100  :  6.64,  in  the  second  as 
100  :  6.58,  and  in  the  third  as  100  :  6.60. 

LAG  OF  ELIMINATION  AFTER  CHANGE  OF  DIET. 

A  considerable  number  of  experiments  upon  the  time  relations  of 
the  elimination  of  nitrogen,  sulphur,  and  phosphorus  after  the  inges- 
tion of  proteid  food  have  recently  been  made  in  the  laboratories  of 
Wesleyan  University0  and  in  the  papers  recording  the  results,  the 
earlier  experiments  upon  this  queston  are  also  discussed.  The  gen- 
eral plan  followed  in  these  studies  is  to  place  the  subject  upon  a 
diet  and  routine  similar  to  that  followed  in  the  first  series  of  experi- 
ments here  recorded,  and  then  to  collect  and  analyze  the  urine  for 
every  three  hours,  or  in  some  cases  every  hour  and  a  half,  during  the 
day,  the  night  urine  being  collected  in  a  single  nine-hour  period. 
The  diet  and  routine  are  strictly  maintained  until  the  urinary  excre- 
tion has  been  found  to  be  practically  uniform  for  two  or  three  days. 
The  subject  then  takes  with  breakfast  either  in  addition  to  the  regu- 
lar food  or  in  place  of  an  isodynamie  amount  of  butter  or  other  food, 
enough  lean  beef  to  furnish  the  desired  amount  of  extra  protein.     All 

"Sherman  and  Hawk.  Amer.  Jour.  Physiol.,  1  (1000) .  p.  25;  Atwater  and  Hawk, 
unpublished  material:  Hawk  and  Chamberlain,  unpublished  material. 


87 

oilier  conditions  remain  unchanged  and  the  urine  is  collected  and 
analyzed  by  Bhorl  periods  as  before,  this  being  kept  up  until  all 
changes  in  the  urine  resulting  from  the  ingestion  of  the  extra 
have  disappeared.  The  tests  made  with  different  subjects  and  in  dif- 
ferent years  show  slight  variations  in  some  details,  but  the  general 
results  agree.  Very  soon  after  the  ingestion  of  the  extra  food  there 
is  a  rise  in  the  rale  of  excretion  of  uitrogen  as  compared  with  that 
found  in  the  corresponding  periods  of  other  days.  This  rise  is  rapid 
and  the  time  required  to  reach  a  maximum  depends  upon  the  amount 


14  0 
130 
120 
1  10 
100 
90 
80 
70 
60 

\ 



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/,.••'' 

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EXPERIMENT    N°  1 
DAvs  1-4. 

EXPERIMENT    N*2 
DAYS  5-8. 

EXPERIMENT    N^3 
DAYS  9-12. 

Fig.  1.— Diagram  showing  fluctuations  in  the  daily  excretion  of  nitrogen  and  phosphorus  during 
the  i\  riments  i  Nos.  1-3).    In  platting  these  curves  the  periods  of  time  are  rep- 

resented by  the  abscissae,  while  the  ordinates  represent  the  excretions  expressed  in  percent- 
ages of  the  average  rate  found  on  the  normal  days.  The  short  horizontal  lines  below  the 
curves  show  the  nights  in  which  the  losses  of  sleep  occurred . 


of  extra  protein  ingested.  With  5  grams  of  extra  nitrogen  the  maxi- 
mum was  reached  in  from  three  to  four  and  one-half  hours;  with  10 
grams,  generally  in  from  six  to  nine  hours.  The  fall  in  the  rate  of 
excretion  was  much  less  rapid  than  the  rise,  but  usually  the  normal 
rate  was  regained  before  the  end  of  the  second  day.  Hie  general 
features  of  the  curve  representing  the  elimination  of  the  extra  nitro- 
gen were  the  same  when  the  subject  was  gaining  as  when  he  was  los- 
ing nitrogen  and  were  the  same  when  the  beef  was  simply  added  to 
the  regular  diet  as  when  it  was  substituted  for  an  isodynamic  amount 
of  butter.     In  general  the  sulphates  and  phosphates  eliminated  were 


38 

Increased  simultaneously  with  the  nil  rogen.  All  of  these  experiments 
had  to  do  with  the  increased  elimination  brought  about  by  the  inges- 
tion of  extra  protein  with  a  single  meal.  Some  of  the  present  experi- 
ments were  arranged  with  a  view  t<>  studying  the  "lag"  in  the  elim- 
ination when  the  diet  was  suddenly  changed  and  the  new  diet 
maintained  for  several  days. 

On  passing  from  the  did  of  experiment  No.  4  to  that  of  experiment 
No.  5,  there  was  little  change  in  fuel  value,  but  the  amounts  of  nitro- 
gen and  phosphorus  ingested  were  largely  increased.  Under  these 
conditions  there  was  a  "lag"  of  some  days,  i.  e.,  some  days  were 
required  before  the  rate  of  elimination  become  approximately  uniform. 
Experiment  No.  4  lasted  three  days  and  although  experiment  No.  5 
properly  continued  but  four  days,  the  diet  was  maintained  and  the 
elimination  of  nitrogen  and  phosphates  determined  for  an  additional 
four  days.  The  course  of  the  excretion  of  nitrogen  and  phosphorus 
for  the  eleven  days  is  shown  in  fig.  2,  in  which  the  curves  are  plat  led 
in  the  same  manner  as  in  fig.  1  above. 

It  will  be  seen  that  while  the  phosphorus  elimination  reaches  a 
maximum  on  the  third  da}",  the  maximum  elimination  of  nitrogen  is 
reached  only  on  the  sixth  day.  It  must  be  noted,  however,  that  the 
increase  of  phosphorus  in  the  diet  was  considerably  greater  in  pro- 
portion than  the  increase  of  nitrogen,  so  that  although  the  curves 
meet  on  the  fifth  da}"  it  does  not  follow  that  equilibrium  was  then 
restored.  When  the  elimination  of  phosphates  was  at  the  maximum 
there  was  a  storage  of  phosphorus  in  the  body,  whereas  during  the 
maximum  elimination  of  nitrogen  the  body  was  losing  that  element. 
The  body  was  in  fact  nearly  in  nitrogen  equilibrium  when  the  maxi- 
mum elimination  of  phosphorus  was  reached. 

In  experiments  Xos.  7  to  10  the  lag  was  studied  under  different  cir- 
cumstances from  those  just  described.  Instead  of  attempting  to  keep 
the  fuel  value  approximately  uniform  while  changing  the  amount  s  of 
certain  constituents,  the  diet  was  here  kept  qualitatively  the  same,  so 
that  every  change  affected  each  of  the  constituents  to  the  same  extent. 
The  general  outline  was  as  follows:  For  five  days  the  subject  took  a 
restricted  diet,  which  it  was  thought,  would  be  just  about  sufficient  to 
enable  him  to  do  his  usual  work  without  becoming  uncomfortably 
hungry.  As  a  matter  of  fact  there  was  practically  no  sensation  of 
hunger,  but  the  subject  lost  during  the  five  days  somewjiat  over  0 
grams  of  nitrogen  and  about  2  pounds  in  weight.  During  a  second 
period  of  five  days  twice  the  original  diet  was  taken.  Then  the  sub- 
ject returned  to  the  original  diet  for  another  period  of  five  days,  the 
object  here  being  to  study  the  lag  after  a  decrease  as  well  as  after  an 
increase  in  the  diet.  At  the  end  of  the  third  period  the  diet  was  again 
doubled,  and  the  double  diet  was  this  time  maintained  for  three  days. 
The  results  for  the  eighteen  days  covered  by  this  series  of  experiments 


39 

are  shown  in  fig.  3,  in  which  t  he  curves  are  platted  in  i  he  same  mannei 
as  in  figs,  l  and  i).  In  this  case  the  sulphate  sulphur  was  also  deter- 
mined, and  is  represented  in  the  figure  bya  broken  line,  nitrogen  and 
phosphorus  being  represented  respectively  by  solid  and  dotted  lines. 
The  rises  and  falls  in  the  curves  in  Ihis  figure  on  passing  from  one 
experimental  period  to  another  are  not  large  as  compared  with  the 


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EXPT.   N°-4. 

EXPERIMENT   N°5. 

DAYS  1  -3. 

DAYS  4-  II. 

Pig.  2.— Diagram  showing  fluctuations  in  the  daily  excretion  of  nitrogen  and  phosphorus  during 
the  second  seriesof  experiments  (Nos.  4  and  6).  The  curves  are  platted  in  the  same  manner 
as  those  in  fig.  1 . 


change  in  the  diet.  Thus  1  lie  diet  in  experiment  No.  8  was  twice  as 
greal  as  in  experiment  No.  7,  but  the  greatest  daily  elimination  was 
only  about  one-half*  larger  for  nitrogen  and  sulphur  and  two-thirds 
larger  for  phosphorus.  This  is  mainly  because,  as  would  bo  expected, 
there  was  a  loss  of  body  material  on  the  small  diet  and  a  gain  on  the 
Large  diets.  The  daily  gains  and  losses  are  shown  in  Table  16,  the 
complete  balance  for  each  experiment  being  tabulated  beyond. 


40 


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41 

As  has  already  been  stated,  the  total  sulphur  and  total  phosphorus 
eliminated  by  the  kidneys  during  each  period  were  determined  by 
analysis  of  a  composite  sample  of  urine.  The  sulphate  Bulphurand 
the  phosphorus  precipitable  by  uranium  acetate  were  determined 
both  in  the  composite  sample  and  in  the  urine  of  each  day.  From 
the  data  thus  found  it  is  easy  to  estimate  the  total  sulphur  or  total 
phosphorus  for  the  urine  of  each  day  if  we  assume  thai  the  ratio  of 
"unOxidized"  to  total  material  is  constanl  during  the  experimental 
period.  While  slighl  errors  mighl  result  from  this -assumption,  they 
would  be  far  too  small  to  affect  i  he  present  discussion.  The  amounts 
thus  estimated  are  therefore  used  in  the  following  table: 


Table  16. 


-Daily  gains  and  losses  of  nitrogen,  sulphur,  and  phosphorus  in  experi- 
ments Nos.  7-10. 


Bzperi 
ment 

num- 
ber. 


10. 


Date. 


July  14-15 

July  15-16 

July  16-17 

July  17-18 

July  18-19 

July  19-20 

July  20-21 

July  21-22 

July  22-23.. ... 

Jul'y  23-24 

July  24  25- 

July  25-26 

July  25-27 

July  27-28 

July  28-29 

July  29-30 

July  30-31 

July  31-Aug.  1 


Nitrogea. 


Sulphur. 


Phosphorus. 


Gain(+) 

Gain(  +  X 

[n  urine. 

or 

loss  (— ). 

In  urine. 

or 

In  urine 

Grams. 

Grams. 

Gram. 

Grams. 

LI.  65 

-   L.99 

0.82 

-0.16 

11.12 

-1.43 

.81 

-  .15 

.92 

11.35 

-1.69 

.87 

-  .21 

1.05 

11.66 

-2 

.82 

-  .16 

1.09 

LI.  75 

-2.09 

.83 

-  .17 

1.05 

14.83 

1.04 

+  .27 

1.23 

15.81 

+3.37 

1.00 

+  .31 

1.48 

15,  L9 

+3. 99 

1.00 

+  .31 

1.47 

14.91 

+4.27 

1.08 

+  .23 

1.65 

us.  m 

+2. 30 

1.16 

+  .15 

1.62 

12.64 

-2.  96 

.89 

-  .23 

1.31 

12.57 

-2.89 

.86 

-  .20 

1.27 

13. 01 

-a.  3b 

.91 

-  .25 

1.43 

12.  73 

-3.05 

.83 

-  .17 

1.31 

12.88 

-3.20 

.90 

-  .24 

1.27 

16.23 

+3.58 

1.19 

+  .07 

1.39 

16.71 

+2.94 

1.23 

+  .03 

1.50 

16.80 

1.22 

+  .04 

1.57 

Gain(+) 

or 
I  «8 


Gram 

+  . 


+  . 
+  . 
+  • 
+  . 


Id 

06 

06 

11 

07 

51 

26 

25 

09 

.12 

23 

.19 

.35 

.19 
.50 

.  32 


It  will  be  seen  from  this  table  that  the  gains  and  losses  were  con- 
siderable, and  that  equilibrium  was  not  reached  in  any  experiment, 
even  after  the  continuance  of  a  uniform  diet  for  five  days.  In  view 
of  the  large  amounts  of  material  gained  and  lost  there  is  danger  that 
any  inferences  in  regard  to  lag  which  could  be  drawn  from  these 
results  might  be  subject  to  unknown  errors  arising  from  the  breaking 
down  of  body  material  on  the  one  hand  or  the  transformation  of  food 
protein  into  body  protein  on  the  other.  It  will  be  shown,  however, 
that,  except  in  cases  where  the  balance  was  evidently  affected  by  the 
lag,  the  proportion  of  sulphur  to  nitrogen  was  nearly  the  same  in  the 
material  stored  or  lost  as  in  the  food  material  actually  absorbed. 
With  phosphorus  the  variations  are  larger,  but  a  similar  relation 
appears  to  exist.  Hence  the  question  of  lag  is  quite  as  important 
here  as  in  the  cases  where  it  has  been  more  especially  studied,  but 
here  it  represents  not  merely  the  time  required  for  the  metabolism  of 
the  ingested  materials,  but  to  some  extent  also  the  time  nece> 
for  the  body  to  adapt  itself  to  the  increased  or  decreased  diet.     On 


42 

passing  from  the  insufficient  diel  of  experimenl  No.  7  to  the  abundant 
did  of  experimenl  No.  8  the  nitrogen  elimination  rises  on  the  first 
day  and  then  remains  nearly  stationary  for  three  days,  during  which 
a  Large  amounl  of  nitrogen  is  stored,  as  though  the  body  during  these 
d;i\  s  was  replacing  the  protein  previously  Lost.  Then  on  the  fifth  day 
the  elimination  again  arises,  though  not  far  enough  to  establish  nitrog- 
enous equilibrium.  The  elimination  of  sulphur  rises  somewhat  more 
sharply  on  the  firsl  day  than  thai  of  nitrogen,  then  continues  about 
uniform  for  two  more  days,  and  begins  to  rise  again  on  the  fourth  day. 
continuing  to  rise  on  the  fifth  and  reaching  a  relative  rate  somewhat 
higher  than  that  of  the  nitrogen.  The  sulphur  curve  is  therefore 
similar  to  the  nitrogen  curve,  but  the  changes  arc  somewhat  more 
marked,  and  in  one  case  appeal'  to  begin  earlier.  The  phosphorus 
rises  sharply  during  the  first  and  second  daysand  again  on  the  fourth 
day.  What  lias  been  suggested  with  reference  to  the  nitrogen  and 
sulphur  appears  to  be  true  to  a  lesser  extent  of  the  phosphorus.  The 
increased  diet  immediately  increases  the  excretion,  the  increase  in 
this  case  continuing  two  days,  then  for  a  short  period — in  this  case 
one  day — the  elimination  is  nearly  constant,  while  a  considerable  pro- 
portion is  stored  in  the  body,  after  which  the  rate  of  elimination  again 
rises.  While  the  phosphorus  does  not  reach  equilibrium  as  regards 
income  and  outgo,  it  more  nearly  approaches  this  condition  than 
either  the  nitrogen  or  the  sulphur. 

When  the  diet  was  reduced  to  one-half,  the  rate  of  elimination  of 
each  of  the  three  elements  studied  fell  sharply  on  the  first  day  and 
showed  little  if  anjr  fall  thereafter.  Thus,  in  each  case  the  eliminat  ion 
lagged  less  in  falling  than  in  rising.  This  is  the  more  striking,  in  view 
of  the  fact  that  the  elimination  of  both  nitrogen  and  sulphur  was 
rising  at  the  time  the  change  in  diet  was  made. 

In  the  final  period,  when  the  double  diet  was  again  resumed,  the 
changes  in  rate  of  elimination  were  similar  to  those  found  in  the  first 
instance,  except  that  the  rise  shown  by  the  sulphur  was  somewhat 
more  pronounced.  Pressure  of  other  work  prevented  the  continuance 
of  this  experiment  after  the  third  day. 

A  somewhat  marked  but  temporary  increase  in  the  phosphorus 
elimination  will  be  noticed  on  the  third  day  of  experiment  No.  9,  and  an 
examination  of  the  curves  shows  that  simultaneously  there  occurred 
a  smaller  but  distinct  increase  of  sulphur,  and  an  increase  of  nitrogen 
which  relatively  is  much  smaller  still  and  would  scarcely  have  been 
noticed  had  only  the  nitrogen  metabolism  been  studied.  Although 
careful  note  had  been  taken  of  anything  which  seemed  likely  to  affect 
metabolism,  it  is  difficult  to  assign  a  reason  for  this  increase.  During 
the  early  parts  of  the  two  preceding  nights  there  had  been  slight  rest- 
lessness, which  was  attributed  to  the  warm  weather,  but  previous 
experiments  had  indicated  thai  simple  loss  of  sleep,  even  when  very 
marked,  had  no  great  influence  upon  the  metabolism  of  this  subject 


43 

and  increased  the  relative  amounl  of  phosphorus  Little,  if  any,  more 
than  that  of  nitrogen.  Such  instances  as  this  would  sec  in  to  lend  some 
support  to  the  view,  apparently  quite  generally  held,  that  the  nervous 
condition  of  the  subject  has  a  greater  influence  upon  the  metabolism 
of  phosphorus  than  upon  thai  of  nitrogen.  A  factorwhich  is  perhaps 
Liable  to  be  overlooked  in  such  cases  is  the  influence  of  the  degree  of 
alkalinity  of  the  blood  upon  the  elimination  of  phosphates  through 
the  kidneys. 

COMPARISON  OF  BALANCE  OF  INCOME  AND  OUTGO. 

It  is  now  generally  recognized  thai  the  daily  balance  of  income  and 
outgo  of  nitrogen  in  the  human  organism  may  be  influenced  hya 

variety  of  factors,  some  of  which  can  not  be  controlled  or  even  satis- 
factorily defined.  The  same  is  doubt  less  1  rue  of  sulphurand  probably 
fed  a  greater  extent  of  phosphorus.     In  general,  it  is  believed  that  in  - 

the  present  experiments  the  metabolism  was  comparatively  free  from 
the  influence  of  such  obscure  factors,  but  in  interpreting  the  figures 
obtained  for  the  balance  we  must  take  into  account  (1)  actual  errors 
in  the  determination  of  income  and  outgo,  and  (2)  the  elimination  on  a 
given  day  of  material  whose  katabolism  is  to  be  attributed  to  the  diet 
or  other  conditions  of  some  preceding  day  or  days — in  other  words, 
the  "lag"  in  the  elimination.  Errors  in  determination  of  income  and 
outgo  fall  into  two  groups — analytical  errors,  and  losses  of  material. 
The  analytical  work  was  carefully  performed  by  the  methods  already 
described.  In  several  cases  the  constituent  sought  was  present  in 
very  small  amount,  which  must  have  increased  the  relative  errors, 
and  it  may  be  stated  that  in  the  opinion  of  the  writer  the  determina- 
tions of  sulphur  were  less  satisfactory  than  those  of  nitrogen  and  of 
phosphorus.  As  regards  the  loss  of  material,  it  is  believed  that  no 
appreciable  mechanical  loss  of  either  food  or  excretory  products  could 
have  occurred  in  any  of  the  experiments,  hut  there  ma}'  have  been 
larger  losses  through  the  perspiration.  As  the  experiments  were  all 
made  in  summer  and  only  one-third  to  one-half  of  the  ingested 
water  appeared  in  the  urine,  considerable  quantities  of  water  must 
have  passed  through  the  skin,  and  more  or  less  loss  of  the  elements 
studied  doubtless  occurred  in  this  way.  The  elimination  of  nitrogen 
through  the  skin  has  been  briefly  discussed  in  a  previous  bulletin," 
where  it  is  shown  that  different  estimates  of  the  amount  which  may  be 
thus  lost  per  day  vary  from  0.2  gram  to  1.36  grams.  Very  little  data 
seems  to  be  available  from  which  to  form  an  idea  of  the  amounts  of 
sulphur  and  phosphorus  which  may  have  been  lost  through  the  skin. 
Favre5  found  in  the  perspiration  only  traces  of  phosphates,  but 
reported  one-fourth  as  much  of  alkaline  sulphates  as  of  urea,  corre- 


«U.  S.  Dept.  Agr.,  Office  of  Experiment  Stations  Bui.  98,  p.  51. 
"Compt.  Rend.  Acad.  Sci.  Paris,  35   (1852),  p.  721;    Schaffer's  Text-book  of 
Physiology,  Vol.  I,  1898;  p.  671. 


44 


sponding  to  an  elimination  by  the  skin  of  about  1  part  by  weight  of 
sulphur  to  8  parts  of  nil  rogen. 

Little  can  be  said  regarding  the  amounts  of  nitrogen  and  sulphur 
given  off  as  volatile  compounds  by  the  intestine  or  Lost  in  drying  the 
feces  in  the  air  at  100°  C.  It  is  known  that  some  nitrogen  is  thus  lost 
from  the  feces,  probably  mainly  as  ammonia.  Loss  of  ammonia  may 
be  avoided  by  adding  acid  before  drying,  but  this  would  result  in  a 
loss  of  sulphur  present  as  sulphids.  Hydrogen  sulphid  is  stated  to 
be  a  normal  constituent  of  the  intestinal  gases,  but  the  amount  of 
sulphur  lost  from  the  body  must  have  been  very  small  in  these  experi- 
ments. It  follows  from  what  has  been  said  that ,  aside  from  any  errors 
of  manipulation  or  analysis,  the  figures  given  for  nitrogen  and  sulphur 
in  urine  and  feces  do  not  quite  represent  the  total  outgo  from  the 
body.  The  average  daily  balance,  as  actually  determined  for  each 
experiment,  is  given  in  Table  17. 

Table  17. — Balance  of  income  and  outgo  of  nitrogen,  sulphur,  and  phosphorus — 

average  per  day. 


Fuel 
value  of 

diet 
per  day. 

Nitrogen. 

Sulphur. 

Phosphorus. 

Experi- 
ment 
number. 

T3 

o 
o 

o  . 

•3,2 
3 

o 
o 

M 

o 

PI 

6 
.2 

8  • 

+2 

pj  m 

o 
o 

Pi 

1— 1 

i 

V 

9 

'u 

u 

o    . 

+1 

iJ 

1. 

2  . 

Calories. 
2, 908 
2,901 
2,913 

2,607 
1,555 
1,660 
3,336 
1,656 
3,329 

Gms. 

15.  82 
15.82 

15.82 
12.05 
18. 52 
9.  76 
10.11 
20.22 
10.11 
20.  70 

Guts. 

0.74 

.  67 

.74 
.  87 
.27 
.45 

1.04 
.43 

1.05 

Gms. 
14.31 

14.67 

14.16 

10.43 
16.  50 
10.94 
11. 51 

15.52 

16.  58 

+0.  77 
+  .48 

+    .'.HI 

+1.15 
-1.45 

+3.66 
-  3. 19 

+3.07 

Gms. 
1.12 
1.12 
1.12 

.  94 
1.44 

.69 

.70 
1.40 

.70 
1.36 

Gm. 

0.06 
.03 
.06 
.09 

.i). 
.02 
.04 
.09 
.04 
.10 

Gms. 

0.95 
.97 
.93 
.72 

1.12 
.75 

1.TO 

.88 
1.21 

Qm. 

+0. 1 1 

+■  .09 

.13 

+  .13 

+  .24 

-  .17 
+  .25 
-  .22 
+  .05 

Gms. 

?..  29 

Gms. 

73 

Gms. 
1.41 
1.48 

1.42 
1.03 
1.74 
1.12 
1.00 
1.49 
1.32 
1.49 

Gm. 
40.10 
+  .08 

3 

2.  29       .  78 
1.40    ■  .44 
3.07     1.10 

+  .09 
-  .07 
+  .23 

4 

5  .. 

6. 

1.60 
1.58 

3.16 
1.58 
3.26 

.37 
.60 

1.42 
.50 

1.37 

+  .11 

-  .02 

8 

9 

10. 

+  .25 

-  .24 
+  .40 

The  first  three  experiments  show  apparent  daily  gains  of  one-half  to 
1  gram  of  nitrogen  and  about  one-tenth  gram  of  sulphur  and  phos- 
phorus. These  apparent  gains  may  be  largely  due  to  the  undetermined 
losses  of  urea,  ammonium  salts,  sulphates  and  phosphates  through 
the  skin,  and  of  volatile  compounds  of  nitrogen  and  sulphur  through 
the  intestines.  In  experiment  No.  5,  in  addition  to  the  sources  of  error 
just  mentioned,  we  have  the  effects  of  "lag"  continuing  through  the 
experiment,  as  explained  above.  Experiment  No.  G  shows  a  moderate 
loss  of  nitrogen  and  a  corresponding  loss  of  sulphur,  but  a  slight 
apparent  gain  of  phosphorus.  In  this  ease,  however,  the  elimination 
of  phosphorus  (as  also  of  nitrogen  and  sulphur)  by  the  intestine  is 
relatively  so  small  as  to  mark  the  experiment  as  somewhat  exceptional. 

It  may  be  said  that  in  these  six  experiments  the  sulphur  balance 
follows  that  of  nitrogen,  but  in  no  ease  is  the  gain  or  loss  great  enough 
to  justify  calculations  of  the  composition  of  the  material  stored  or 
broken  down. 


45 

In  experiments  Nos.  7,  8,  and  9  the  gains  and  losses  are  Larger,  and 
here  it  is  probably  safe  i<>  draw  inferences  regarding  t be  composil  ion 
of  the  materia]  stored  or  lost  by  the  body,  though  the  undetermined 
errors  already  discussed  will  of  course  affecl  the  accuracy  of  such 
deductions.  Neglecting  these  errors,  the  figures  given  for  ■•  balance" 
would  Indicate  thai  in  the  materia]  lost  in  the  first  of  these  experi- 
ments ilic  ratio  of  sulphur  to  nitrogen  was  as  I  :10.9,  in  thai  stored  in 
the  second  as  1:14.6,  and  in  thai  lost  in  the  third  as  1 :  14.  The  ratio 
in  the  food  consumed  was  L:14.4,  in  the  food  material  actually  absorbed 
(food  minus  feces)  it  was  1:14.6.  It  was  calculated  above  that  this 
ratio  in  serum  globulin  is  L-.14.3,  in  myosin  1  :13.1,  in  serum  albumin 
L:7.1,  and  in  the  glycoproteids  of  connective  tissue  and  of  bone  as 
about  1:5.  Thus  the  ratio  is  narrower  in  the  tissue  proteids  gener- 
ally than  in  the  food  here  consumed,  but  in  serum  globulin  the  ratio 
is  about  the  same,  and  in  myosin  not  greatly  different.  A  strict  inter- 
pretation of  these  ratios  would  thus  lead  to  the  conclusion  that  in  the 
first  period  the  body  metabolized  the  food  eaten  and  some  of  its  own 
material  in  which  the  ratio  is  narrower;  that  in  the  second,  a  part  of 
the  protein  of  the  food  is  either  stored  without  essential  change  or  con- 
verted for  storage  into  some  form  of  body  protein  in  which  the  ratio  is 
practically  the  same  (as  in  the  case  with  serum  globulin),  and  that 
the  proteid  lost  in  the  third  period  was  of  the  same  nature  as  that 
stored  in  the  second  period.  Such  a  method  of  interpretation  is  in  line 
with  that  followed  by  Kolpatcka  in  his  studies  upon  dogs,  but  for  the 
reasons  already  given  it  is  believed  that  such  conclusions  must  be 
accepted  with  reserve  until  more  is  known  of  the  conditions  influencing 
the  "balance"  and  the  "lag."  These  experiments,  however,  do  at 
any  rate  strongly  emphasize  the  close  parallelism  between  the  meta- 
bolism of  nitrogen  and  that  of  sulphur  when  the  diet  is  normal  and  is 
continued  uniform  for  a  period  long  enough  to  practically  eliminate 
the  effects  of  the  lag.  In  experiment  Xo.  10,  which  continued  but  three 
days,  the  balance  is  much  influenced  by  the  lag,  so  that  in  this  case 
the  apparent  gains  show  no  relation  to  the  proportions  of  the  two 
elements  in  the  food. 

On  the  other  hand  the  phosphorus  metabolism  does  not  show  such  a 
close  parallelism  to  the  metabolism  of  nitrogen.  In  experiment  Xo.  7, 
where  the  loss  of  nitrogen  was  nearly  constant  throughout,  there  was 
at  first  a  slight  gain  and  later  a  slight  loss  of  phosphorus,  the  net 
result  being  an  almost  perfect  balance.  This  is  probably  due  to  the 
comparative  richness  of  the  diet  in  phosphorus,  so  that  it  supplied 
sufficient  of  this  element  for  the  needs  of  the  body,  while  the  protein 
of.  the  diet  was  so  far  insufficient  as  to  result  in  considerable  loss  of 
nitrogen  and  sulphur.  During  the  live  days  of  abundant  diet  (experi- 
ment Xo.  8)  there  was  a  storage  of  1.25  grams  of  phosphorus,  and 
almost  exactly  the  same  amount  was  given  up  during  the  following 
five  days  of  restricted  diet.     The  three  days  of  experiment  No.  10 


4o 

show  a  large  apparent  gain  of  phosphorus,  but  this  is  largely  due  to 
the  "v  Lag"  and  can  not  be  considered  to  represent  permanently-stored 
material. 

Any  comparison  of  the  nitrogen  and  phosphorus  metabolism  in  the 
human  organism  is  complicated  by  the  varying  proportions  of  phos- 
phorus eliminated  in  the  feces.  Thus  in  experiments  Nos.  8  and  9the 
diet  was  qualitatively  the  same,  ye1  in  the  former  44.9  per  cent  and  in 
1  lie  latter  only  31.6  per  eenl  of  the  phosphorus  in  the  food  was  found  in 
I  lie  feces.  Two  explanations  suggest  themselves,  (1)  thai  only  a  part 
of  the  phosphates  from  body  katabolism  may  appear  in  the  urine,  the 
remainder  being  eliminated  through  the  intestine,  as  in  the  herbivo- 
rous animals;  (2)  that  the  proportion  which  the  body  absorbs  may 
depend  not  only  upon  the  nature  of  the  ingested  phosphates,  but  also 
upon  the  condition  and  needs  of  the  body.  The  former  is  probably 
true  to  some  extent,  but  it  seems  probable  that  the  latter  also  oper- 
ates in  some  cases,  as  in  that  just  mentioned,  where,  on  doubling  the 
diet,  a  much  smaller  proportion  of  the  phosphorus  present  was  assim- 
ilated. 

The  larger  proportion  of  ingested  phosphorus  which  appears  in  the 
feces  makes  the  proper  separation  of  the  latter  a  much  more  impor- 
tant matter  in  experiments  in  which  the  balance  of  phosphorus  is  to  be 
determined  than  in  those  in  which  onty  nitrogen  or  nitrogen  and 
sulphur  are  studied. 

In  view  of  the  results  which  have  recently  been  obtained  upon  the 
assimilation  of  the  phosphorus  of  casein/'  the  phosphates  found  in 
the  feces  in  these  experiments  should  probably  be  attributed  mainly 
to  the  calcium  phosphate  of  the  food.  It  should  be  remembered  also 
that  in  the  present  experiments  the  diet  was  unusually  rich  in  phos- 
phates, and  the  proper  interpretation  of  the  results  must  await  the 
completion  of  similar  experiments  upon  different  diets. 

The  experiments  here  reported  afford  no  data  for  a  direct  compari- 
son of  the  nutritive  values  of  different  proteids,  the  food  materials 
used  having  been  similar  through  the  whole  series.  However,  in  view 
of  the  recent  work  upon  the  nutritive  value  of  the  proteids  of  milk,6 
it  is  interesting  to  note  the  tendency  shown  in  experiments  Nos.  1  to 
4  to  store  protein  on  a  diet  considerably  smaller  than  that  usually 
estimated  for  a  subject  of  vigorous  appetite  and  doing  a  considerable 
amount  of  work. 

«Marcuse,  Arch. Physiol.  [Pfliiger],  G7  (1897),  p.  373;  Knopf  elm  acher,  Wiener 
Klin.  Wchnschr.,  12  (1899),  p.  1308;  Nicko.  Ztschr.  Biol.,  39  (1900),  p.  430; 
Miiller,  Ibid.,  p.  451. 

b Among  the  many  recent  papers  may  be  noted:  Marcuse,  Arch.  Physiol. 
[Pfliiger] ,  64  (1896) ,  p.  223;  Steinitz,  Ibid..  72'  (1898) .  p.  75;  Rohmann,  Berl.  Klin. 
Wchnschr.,  35  (1898),  p.  789;  Albn,  Fortschr.  Med.,  17  (1899),  p.  505:  Poda  and 
Prausnitz,  Ztschr.  Biol.,  39  (1899-1900).  p.  279. 


IT 

SUMMARY. 

The  digestibility  of  the  protein  of  the  bread  and  milk  diel  as  found 
ni  nine  of  the  teD  experiments  agreed  closely  with  the  results  calcu- 
lated, assuming  97  per  cenl  as  the  coefficienl  for  milk  and  90 per  cent 
as  that  for  bread.     The  digestibilityjwas  nol   appreciably  influenced 

by    loss  of  sleep    nor   by    the   eont  in  nance   of  the   diet    lor  twelve    or 

eighteen  days. 

The  proportions  of  protein  digested  from  a  restricted  diet  were 
about  0. 7  per  ceiit  higher  than  those  digested  from  a  liberal  diet  of 
the  same  composition. 

.Marked  loss  of  sleep  for  three  successive  nights  resulted  in  a  small 
increase  in  the  amounts  of  nitrogen,  sulphur,  ami  phosphorus  excreted. 
The  increase  of  sulphur  was  proportional  to  that  of  nitrogen  and  the 
increase  of  phosphorus  was  wry  slighl  ly  larger,  the  relal  ive  difference 
being  no  greater  than  might  be  attributed  to  the  usual  daily  varia- 
tions. 

The  increased  elimination  resulting  from  loss  of  sleep  did  not  appear 
until  the  third  day,  while  changes  resulting  from  alteration  of  the  diet 
were  always  perceptible  on  tin1  first  day. 

The  data  collected  regarding  the  relative  "lag"  of  nitrogen,  sul- 
phur, and  phosphorus  are  not  j^et  sufficient  to  permit  general  conclu- 
sions to  be  drawn. 

In  general  the  metabolism  and  "balance"  of  sulphur  ran  approxi- 
mately parallel  with  that  of  nitrogen. 

The  renal  elimination  and  "balance"  of  phosphorus  showed  fluctu- 
ations similar  to  those  of  nitrogen,  but  not  so  closely  parallel  as  in 
the  case  of  sulphur.  The  elimination  of  phosphorus  by  the  intestine 
was  large  and  variable,  making  the  accurate  separation  of  the  feces 
an  important  factor  in  the  determination  of  the  phosphorus  balance. 

The  above  statements  are  intended  merely  to  summarize  the  results 
of  the  experiments  here  reported.  As  these  were  all  made  upon  a 
single  subject  and  with  only  two  orthreefood  materials,  it  would  obvi- 
ously be  unsafe  to  generalize  broadly  from  the  results.  As  already 
explained,  the  work  was  undertaken  not  so  much  with  a  view  to  obtain- 
ing results  of  intrinsic  interest  as  to  get  data  regarding  methods  of 
work  and  possible  sources  of  error,  and  thus  facilitate  the  stud}r  of  the 
sulphur  and  phosphorus  metabolism  in  connection  with  certain  of  the 
series  of  nutrition  investigations  to  which  the  present  experiments 
belong. 

O 


LIST  OF  PUBLICATIONS  OF  THE  OFFICE  OF  EXPERIMENT   STATIONS  ON 
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Bui.  tw.  a  Description  of  Some  Chin  ble  Food  Materials  and  Their  Nutritive  and 

Economic  Value.    By  W.  C.  Blasdale     1|  10  cents. 

Bui.  69,  Experiments  on  the  Metabolism  of  Matter  and  Energy  in  the  Hainan  Body.    ByW.O. 

Atwater  and  F.  Gh  Benedict,  with  the    ooperatioa  of  .\.  W.  Smith  and  A   !\  Bryant 

Pp.  ii:.'.    Price,  10 cents. 
Bui.  71.  Dietary  Studie  rxj  Virginia  in  L89*i  11  and 

[sabel  BerieT.    Pp.46.    Price,  5  cents. 
Bol.  75.  Dietary  Studies ol  University  Boat  Crews.    By  W.  O.  Atwater  and  A.  1'.  Bryant     Pp. 

QtS. 

Hnl. -i.  Nutrition Investigations  at  the  California  Agricultural  Experimenl  station.  1896 
By  H.  E.  Jaffa.    Pp.  30.  .  Price,  5  cents 

Bui.  85.  A  Report  of  Investigations  on  the  Digestibility  and  Nutritive  Value  >>f  Bread.  By 
('has.  1).  Woods  and  Li.  H.  Merrill.    Pp.  51.    Price,  Scents. 

Bui.  89.  Experiments  on  the  Effect  of  Muscular  Work  upon  the  Digestibility  of  Pood  and  the 
Metabolism  of  Nitrogen.  Conducted  at  the  Universityof  Tennessee,  L897  \^'v.  By 
C.  E.  Wait.    Pp.  77.    Price,  5  cents. 

Bui.  91.  Nutrition  Investigations  at  the  Universityof  Illinois,  North  Dakota  Agricultural  Col- 
lege*, and  Lake  Erie  College,  Ohio,  IBOfc  1900.  By  H.  S.  Crindley  and  J.  L.  Sanmns.  E. 
P.  Ladd,  and  Isabel  Bevier  and  Elizabeth  C.  Sprague.     Pp.  12.     Price,6  COtttS. 

Bui.  98.  The  Effect  of  Severe  and  Prolonged  Muscular  Work  on  Food  Consumption,  Digestion, 
and  Metabolism,  by  W.  O.  Atwater  and  H.  C.  Sherman,  and  the  Mechanical  Work  and 
Efficiency  of  Bicyclers,  by  R.  C.  Carpenter.    Pp.  <">7.     Price.  .">  cents. 

Bui.  101.  Studies  on  Bread  and  Bread  Making  at  the  University  of  Minnesota  in  1899  and  1900. 
By  Harry  Snyder.     Pp.  to.     Price,  5  cenrs. 

Bui.  102.  Experiments  on  Losses  in  Cooking  Meat.  isits-  1900.  By  H.  S.  Grindley,  with  the  coop- 
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Bui.  107.  Nutrition  Investigations  Among  Fruitarians  and  Chinese  at  the  California  Agricul- 
tural Experiment  Station.  1899-1901.     By  M.  E.  Jaffa.    Pp.  48.     Price.  5  cents. 

Bui.  KJfl.  Experiments  on  the  Metabolism  of  Matter  and  Energy  in  the  Human  Body.  1896-1900. 
By  W.  O.  Atwater  and  F.  G.  Benedict,  with  the  cooperation  of  A.  P.  Bryant,  A.  W. 
Smith,  and  J.  F.  Snell.    Pp.  147.    Price,  10  cents. 

Bui.  116.  Dietary  Studies  in  New  York  City  in  1896  and  1897.  By  W.  O.  Atwater  and  A.  P.  Bry- 
ant.    Pp.  83.     Price,  5  cents. 

Bui.  117.  Experiments  on  the  Effect  of  Muscular  Work  upon  the  Digestibility  of  Food  and  the 
Metabolism  of  Nitrogen.  Conducted  at  the  University  of  Tennessee,  1899-1900.  By 
Chas.  E.  Wait.    Pp.  48.    Price,  5  cents. 

FARMERS'    bUIilitTTlNS. 

*  Bui.  23.  Foods:  Nutritive  Value  and  Cost     By  W.  O.  Atwater.    Pp.  32. 

Bui.    34.  Meats:  Composition  and  Cooking.    By  C.  D.  Woods.    Pp.29. 

Bui.    74.  Milk  as  Food.    Pp.  39. 

Bui.    85.  Fish  as  Food.    By  C.  F.  Langworthy.    Pp.  30. 

Bill.    93.  Sugar  as  Food.    By  Mary  H.  Abel.    Pp.  27. 

Bui.  112.  Bread  and  the  Principles  of  Bread  Making.    By  Helen  W.  Atwater.    Pp.  39. 

Bid.  121.  Beans,  Peas,  and  other  Legumes  as  Food.    By  Mary  H.  Abel.    Pp.  32. 

Bui.  128.  Eggs  and  their  Uses  as  Food.    By  C.  F.  Langworthy.    Pp.  32. 

Bui.  142.  Principles  of  Nutrition  and  Nutritive  Value  of  Food.    By  W.  O.  Atwater.    Pp.  48. 

CIHCrLAli. 

Cir.    46.  The  Functions  and  Uses  of  Food.    By  C.  F.  Langworthy.    Pp.10. 

B]   I'AWATK.s. 

♦Food  and  Diet.  By  W.  O.  Atwater.  Reprinted  from  Yearbook  of  Department  of  Agriculture 
for  1894.    Pp.  44. 

Some  Results  of  Dietary  Studies  in  the  United  States.  By  A.  P.  Bryant.  Reprinted  from  Year- 
book of  Department  of  Agriculture  for  1898.    Pp.  14. 

Development  of  the  Nutrition  Investigations  of  the  Department  of  Agriculture.  By  A.  C.  True 
and  R.  D.  Milner.  Reprinted  from  Yearbook  of  Department  of  Agriculture  for  1899. 
Pp.  it;. 

The  Value  of  Potatoes  as  Food.  By  C.  F.  Langworthy.  Reprinted  from  Yearbook  of  Depart- 
ment of  Agriculture  for  1900.    Pp.  16. 

Dietaries  in  Public  Institutions.  By  W.  O.  Atwater.  Reprinted  from  Yearbook  of  Department 
of  Agriculture  for  1901.    Pp.  18. 

Scope  and  Results  of  the  Nutrition  Investigations  of  the  Office  of  Experiment  Stations. 
Reprinted  from  Annual  Report  of  the  Office  of  Experiment  Stations  for  the  year  ended 
June  30, 1901.    Pp.  50. 


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